Back to blog
Research

APIs Explained: How They Power Software and Crypto

Understand what an API is, how APIs work, common protocols like REST and GraphQL, and practical considerations for crypto and AI integrations.
Token Metrics Team
5
Want Smarter Crypto Picks—Free?
See unbiased Token Metrics Ratings for BTC, ETH, and top alts.
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
 No credit card | 1-click unsubscribe

APIs are the invisible connectors that let apps talk to each other. Whether you’re loading a weather widget, pulling crypto prices into a dashboard, or integrating an AI model, understanding how APIs work helps you design, evaluate, and secure systems that depend on reliable data.

What is an API?

An API—Application Programming Interface—is a clearly defined set of rules and contracts that lets one software program request services or data from another. At its core an API specifies how to format requests, what endpoints are available, what parameters are accepted, and how the provider will respond. Think of it as a menu at a restaurant: you pick dishes (requests), the kitchen prepares them (the service), and the waiter returns your order (the response) without exposing internal cooking processes.

APIs exist at many levels: operating system APIs expose filesystem and device operations, library APIs expose functions and classes, and web APIs expose remote services across networks. In modern web and mobile development, "API" often refers to HTTP-based interfaces that return structured data like JSON or XML.

How APIs Work: Requests, Responses, and Data Formats

Most web APIs operate on a request–response model. A client issues a request to a defined endpoint using a method (GET, POST, PUT, DELETE), optionally supplying parameters or a payload. The server processes the request and returns a response with a status code and body.

Key technical elements to understand:

  • Endpoints: URLs that map to resources or actions (e.g., /v1/prices).
  • HTTP Methods: Semantic actions (GET = read, POST = create, etc.).
  • Status Codes: 2xx successes, 4xx client errors, 5xx server errors.
  • Data Formats: JSON is ubiquitous for APIs due to its simplicity; XML and protobufs appear in legacy or high-performance systems.
  • Authentication & Authorization: API keys, OAuth tokens, JWTs, and mTLS govern who can access which endpoints.
  • Rate Limits & Quotas: Providers throttle requests to protect infrastructure and ensure fair use.

Real-time APIs may use WebSockets or server-sent events for streaming data rather than repeated HTTP polling. Designing for observability—clear logs, metrics, and error messages—improves operational resilience.

Common API Types and Protocols

Different projects require different API styles. Choosing a style depends on latency, flexibility, compatibility, and developer experience needs.

  • REST: Representational State Transfer emphasizes resources and standard HTTP verbs. RESTful APIs are easy to cache and widely supported.
  • GraphQL: Clients request exactly the fields they need in a single query, reducing over-fetching. GraphQL adds flexibility but requires careful performance tooling.
  • SOAP: An XML-heavy protocol that offers strict contracts and built-in standards for security and transactions; common in enterprise systems.
  • gRPC / Protobuf: High-performance RPC frameworks for microservices with compact binary payloads and strict typing.
  • Webhooks: Reverse-style APIs where a service pushes events to your endpoint, useful for near-real-time notifications without polling.

APIs are often packaged with SDKs for languages like Python, JavaScript, or Go to simplify integration. Documentation, example requests, and interactive consoles dramatically improve adoption.

APIs in Crypto and AI: Use Cases and Considerations

APIs are central to crypto and AI ecosystems. In crypto, APIs provide market data (prices, order books), on-chain insights (transaction history, token balances), and node RPC endpoints for smart contract interaction. AI systems use APIs to host inference endpoints, orchestrate models, and integrate external data sources for context.

Key considerations when selecting or building APIs for these domains:

  • Data Accuracy: In finance and blockchain, stale or inconsistent data can lead to incorrect analysis. Verify timestamps, aggregation logic, and reconciliation methods.
  • Latency and Throughput: Trading or real-time analytics may require low-latency streaming or websocket feeds instead of periodic REST calls.
  • Security: Protect API keys, enforce least privilege, use encrypted transport (HTTPS/TLS), and monitor for anomalous request patterns.
  • Reliability: Redundancy, caching strategies, and graceful degradation help maintain service if a provider faces outages.
  • Compliance & Privacy: Understand data retention, user privacy, and jurisdictional constraints when handling labeled or personal data.

Tools like Token Metrics combine market and on-chain data with AI to support research workflows that depend on reliable API feeds and model-driven signals.

Build Smarter Crypto Apps & AI Agents with Token Metrics

Token Metrics provides real-time prices, trading signals, and on-chain insights all from one powerful API. Grab a Free API Key

What is the difference between REST and GraphQL?

REST exposes multiple endpoints representing resources; clients may need several calls to assemble data. GraphQL exposes a single query endpoint where clients request precisely the fields they need. REST is simpler to cache; GraphQL offers flexibility but can require extra server-side tooling to manage complex queries and performance.

How do I secure an API key?

Never embed keys in client-side code. Store keys in secure server environments or secrets managers, rotate keys periodically, apply scope and rate limits, and monitor usage. Implementing short-lived tokens and IP whitelisting adds protection for sensitive endpoints.

When should I use webhooks instead of polling?

Use webhooks when you need event-driven, near-real-time notifications and want to avoid the overhead of frequent polling. Webhooks push updates to your endpoint, but require you to handle retries, verify payload signatures, and secure the receiving endpoint.

Can I build an API for my blockchain node?

Yes. Many projects wrap node RPCs with REST or GraphQL layers to standardize queries and add caching, rate limiting, and enrichment (e.g., token metadata). Be mindful of node sync status, resource consumption, and privacy considerations when exposing node endpoints.

How do I evaluate an API provider?

Assess API documentation quality, uptime/SLAs, latency, data freshness, authentication options, and support channels. Request sample data, test in sandbox environments, and compare pricing with expected usage. For crypto use cases, verify on-chain data coverage and reconciliation methods.

Disclaimer

This article is for educational purposes and does not constitute investment advice or recommendations. Evaluate APIs, platforms, and tools against your own requirements and compliance obligations before use.

Build Smarter Crypto Apps &
AI Agents in Minutes, Not Months
Real-time prices, trading signals, and on-chain insights all from one powerful API.
Grab a Free API Key
About Token Metrics
Token Metrics: AI-powered crypto research and ratings platform. We help investors make smarter decisions with unbiased Token Metrics Ratings, on-chain analytics, and editor-curated “Top 10” guides. Our platform distills thousands of data points into clear scores, trends, and alerts you can act on.
30 Employees
analysts, data scientists, and crypto engineers
30 Employees
analysts, data scientists, and crypto engineers
30 Employees
analysts, data scientists, and crypto engineers
Want Smarter Crypto Picks—Free?
See unbiased Token Metrics Ratings for BTC, ETH, and top alts.
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
 No credit card | 1-click unsubscribe
Token Metrics Team
Token Metrics Team

Recent Posts

Research

Top 100 Crypto Index: What It Is, How It’s Built, and Who It’s For (2025)

Token Metrics Team
6

If you’ve tried to “own the market” in crypto, you’ve felt the pain: chasing listings, juggling wallets, and missing rebalances while prices move. A top 100 crypto index aims to fix that—giving you broad exposure when the market is bullish and standing down when it’s not. Token Metrics Global 100 is our rules-based version of that idea: it holds the top-100 by market cap in bull regimes, moves to stablecoins in bear regimes, and rebalances weekly. You can see every rule, every holding, and every rebalance—then buy the index in ~90 seconds with an embedded on-chain flow.‍ → Join the waitlist to be first to trade TM Global 100.

Why a “Top 100 Crypto Index” Matters in October 2025

The market keeps cycling. New leaders emerge quickly. A “set-and-forget” bag can fall behind, while manual baskets burn hours and rack up slippage. Search interest for crypto index, regime switching, and weekly rebalancing keeps growing because people want a simple, disciplined core that adapts.

A top 100 crypto index is a rules-based basket that tracks the largest 100 crypto assets by market cap, typically rebalanced on a schedule to keep weights aligned with the market. In 2025, that alone isn’t enough. You also need discipline for downtrends. Token Metrics adds a regime-switching layer to move to stablecoins during bear phases—so you can participate in upside and sit out major drawdowns with a consistent, rules-based approach.

How the TM Global 100 Index Works (Plain English)

Regime switching:

  • Bullish: The index holds the top-100 assets by market cap.
  • Bearish: The index exits positions and moves fully to stablecoins until a bullish re-entry signal.

Weekly rebalancing:

  • Every week, the composition and weights update to reflect current market-cap rankings. No manual list maintenance. No “oops, I missed the new entrant.”

Transparency:

  • Strategy modal explains selection criteria and regime logic.
  • Gauge → Treemap → Transactions Log shows the signal, the real-time holdings view, and every rebalance/regime switch.

You’ll always see what you own, how it changed, and why.

What you’ll see on launch

  • Price tile, 100 tokens, “rebalances weekly,” and one-click Buy.
  • Gauge to visualize the market signal.
  • Holdings Treemap and Table to inspect exposure.
  • Transactions Log to review every rebalance.
  • See the strategy and rules.

Benefits at a Glance (Why This Beats DIY)

  • Time saved: Skip hours of asset chasing and manual spreadsheets; rebalances happen automatically.
  • Lower execution drag: One index buy can reduce slippage vs. piecing together 20–50 small orders across chains.
  • Never miss a rebalance: Weekly updates and on/off risk switches run by rules, not vibes.
  • Rules-based switching: A clear trigger defines when to sit in stablecoins—no second-guessing.
  • Full visibility: The gauge, treemap, table, and log make the process auditable at a glance.
  • Operational simplicity: An embedded wallet, 90-second buy flow, fee and slippage estimates upfront.

Step-by-Step: How to Get Early Access (Waitlist)

  1. Open the Indices hub and tap TM Global 100.
  2. Join the waitlist with your email—this flags you for day-one access.
  3. (Optional) Connect your wallet so you’re ready for the embedded checkout.
  4. Launch day: You’ll get an email and in-app prompt when trading opens.
  5. Buy in ~90 seconds: Connect, review fees/slippage/estimated value, confirm.
  6. Track positions: See your holdings, rebalances, and P&L in My Indices.
  7. Repeat or add funds: Rebalancing is handled weekly; you can add or sell anytime.

→ Join the waitlist to be first to trade TM Global 100.

Decision Guide: Is This Right for You?

  • Hands-Off Allocator: Want broad market exposure without managing coin lists? Consider it.
  • Active Trader: Want a disciplined core you don’t have to watch while you chase setups? Consider it.
  • TM Member (Research-Heavy): Prefer to keep your picks, but want a market base layer? Consider it.
  • New to Crypto: Need transparency + clear rules? Consider it, with a small test first.
  • Hyper-Niche Maxi: If you only want 1–2 coins, an index may be too broad.
  • Short-Term Scalper: You may still benefit from a core allocation, but active trading stays your main driver.
  • Tax-/Jurisdiction-Sensitive Users: Check your local rules before investing.
  • Institutional Explorers: Looking for transparent rules, logs, and weekly governance? Worth evaluating.

FAQs

What is a top 100 crypto index?

A rules-based basket tracking the largest 100 assets by market cap, typically with scheduled rebalancing. Token Metrics Global 100 adds regime switching to stablecoins during bear markets.

How often does the index rebalance?

Weekly. In addition, if the market signal flips, the entire portfolio may switch between tokens ↔ stablecoins outside the weekly cycle.

What triggers the move to stablecoins?

A proprietary market-regime signal. When it’s bearish, the index exits tokens to stablecoins and waits for a bullish re-entry signal.

Can I fund with USDC or fiat?

On launch, funding options surface based on your connected wallet and supported chains. USDC payouts are supported when selling.

Is the wallet custodial?

The embedded wallet is self-custodial—you control your funds.

How are fees shown?

Before you confirm a buy, you’ll see estimated gas, platform fee, max slippage, and minimum expected value—all up front.

How do I join the waitlist?

Go to the TM Global 100 page or the Indices hub and click Join Waitlist. You’ll get notified at launch with simple steps to buy.

Security, Risk & Transparency

  • Self-custody: Embedded, self-custodial smart wallet; you control keys.
  • 2FA & device checks: Standard authentication best practices.
  • Fee/slippage transparency: All estimates are shown pre-trade; you confirm with eyes open.
  • On-chain visibility: Holdings, rebalances, and regime switches appear in the Transactions Log.
  • Rule constraints: Signals can be wrong; spreads and volatility can impact outcomes.
  • Regional considerations: Availability and tax treatment vary by jurisdiction.

Crypto is volatile and can lose value. Past performance is not indicative of future results. This article is for research/education, not financial advice.

A top 100 crypto index is the simplest path to broad market exposure—if it’s built with discipline. Token Metrics Global 100 combines transparent rules, weekly rebalancing, and a regime switch to stablecoins, so you can focus on your strategy while the core maintains itself. Now’s the time to claim early access.‍ → Join the waitlist to be first to trade TM Global 100.

Research

The Case for Rules-Based Crypto Indexing After a Volatile Cycle (2025)

Token Metrics Team
5

After a whipsaw year, many investors are asking how to stay exposed to crypto’s upside without riding every drawdown. Rules-based crypto indexing is a simple, disciplined answer: follow a transparent set of rules rather than gut feelings. The Token Metrics Global 100 puts this into practice—own the top-100 in bullish regimes, rotate to stablecoins in bearish regimes, and rebalance weekly. On top of that, you can see what you own in real time with a Holdings Treemap, Table, and Transactions Log. Less second-guessing, more process.

→ Join the waitlist to be first to trade TM Global 100.

Why Rules-Based Crypto Indexing Matters in October 2025

In a volatile cycle, emotion creeps in: chasing winners late, cutting losers early, or missing re-entry after fear. Rules-based crypto indexing applies consistent criteria—constituent selection, weighting, and rebalancing—so you don’t have to improvise in stress.

For readers comparing crypto index options, think of it as a codified playbook. A rules-based crypto index is a methodology-driven basket that follows predefined signals (e.g., market regime) and maintenance schedules (e.g., weekly rebalancing), aiming for repeatable behavior across cycles.

Rules-based crypto indexing is a systematic approach that tracks a defined universe (e.g., top-100 by market cap) and maintains it on a fixed cadence, with explicit rules for when to hold tokens and when to de-risk into stablecoins.

How the TM Global 100 Index Works

  • Regime switching: When the market signal is bullish, the index holds the top 100 assets by market cap; when bearish, it moves to stablecoins until conditions improve.
  • Weekly rebalancing: Constituents and weights update weekly to reflect the latest market-cap rankings—capturing leadership changes without manual effort.
  • Transparency: A Strategy modal and Gauge → Treemap → Transactions Log show the signal, current mix, and every change recorded.

What you’ll see on launch: Price tile, “tokens: 100,” “rebalances weekly,” and a fast ~90-second Buy flow with fee/slippage previews.

See the strategy and rules. (TM Global 100 strategy)

Benefits at a Glance (Why This Beats DIY)

  • Time & operational drag: Skip juggling 20–100 tickers, wallets, and venues.
  • Execution quality: A single indexed flow can help reduce piecemeal slippage and duplicated fees.
  • No missed rotations: Weekly rebalancing and regime switching reduce the cost of being late to trends—or late to de-risk.
  • Always-on visibility: Holdings treemap + table + transactions log remove the black box.
  • Behavioral edge: Clear rules can limit panic sells and FOMO buys during turbulence.
  • Portfolio role: A disciplined core that you can complement with selective satellites.

Step-by-Step: How to Get Early Access (Waitlist)

  1. Open the Token Metrics Indices hub and select TM Global 100.
  2. Click Join Waitlist and enter your email for launch-day access.
  3. (Optional) Connect your wallet so you’re ready to fund.
  4. On launch, review the Gauge → Treemap → Transactions to confirm the current mix.
  5. Tap Buy Index, review fees/slippage, and confirm (about 90 seconds end-to-end).
  6. Track your position and every weekly rebalance in My Indices and the Transactions Log.

→ Join the waitlist to be first to trade TM Global 100.

Decision Guide: Is This Right for You?

  • Hands-Off Allocator: Want broad market beta with an explicit de-risking rule. Consider if you resist micromanaging.
  • Active Trader: Prefer a disciplined core that moves to stablecoins in bears while you express edge with satellites.
  • Long-Term Believer: Seek systematic participation in leadership changes via weekly rebalancing.
  • Transparency-First User: Require auditable holdings and a transactions log—no black boxes.
  • Tax/Compliance Conscious: Prefer consolidated rebalances over many ad hoc trades.
  • TM Research Follower: Want to pair Token Metrics insights with a rules-based execution layer.
  • New to Crypto Baskets: Want to avoid building and maintaining a DIY index.

FAQs

What is a rules-based crypto index?

A methodology-driven basket that follows predefined rules for asset selection, weighting, and maintenance. In TM Global 100, that means top-100 exposure in bullish regimes and stablecoins in bearish regimes, with weekly rebalancing and full transparency.

How often does the index rebalance?

Weekly. This cadence refreshes constituents and weights to align with current market-cap rankings; separate regime switches can move between tokens and stablecoins.

What triggers the move to stablecoins?

A documented market signal. When it turns bearish, the index exits to stablecoins; when bullish resumes, it re-enters the top-100 basket.

Can I fund with USDC or fiat?

Funding options will surface based on your connected wallet and supported rails. USDC settlement on sells is supported; fiat on-ramps may be added over time.

Is the wallet custodial?

No. The embedded wallet is self-custodial—you control your keys and assets.

How are fees shown?

Before confirming a trade, you’ll see estimated gas, platform fee, max slippage, and min expected value—so you can proceed with clarity.

How do I join the waitlist?

Go to the Indices hub, open TM Global 100, and enter your email. You’ll receive a launch-day link to buy.

Security, Risk & Transparency

  • Self-custody by default: You control your wallet.
  • Defense-in-depth: 2FA/account security features and explicit transaction prompts.
  • Clear economics: Fee and slippage previews before you confirm.
  • Auditability: Holdings treemap + table + transactions log document every change.
  • Methodology limits: Regime logic may not capture every market nuance; weekly cadence can differ from intraday moves.
  • Regional availability: On-ramps and features can vary by jurisdiction.

Crypto is volatile and can lose value. Past performance is not indicative of future results. This article is for research/education, not financial advice.

Research

The Case for Rules-Based Crypto Indexing After a Volatile Cycle (2025)

Token Metrics Team
5

After a whipsaw year, many investors are asking how to stay exposed to crypto’s upside without riding every drawdown. Rules-based crypto indexing is a simple, disciplined answer: follow a transparent set of rules rather than gut feelings. The Token Metrics Global 100 puts this into practice—own the top-100 in bullish regimes, rotate to stablecoins in bearish regimes, and rebalance weekly. On top of that, you can see what you own in real time with a Holdings Treemap, Table, and Transactions Log. Less second-guessing, more process.→ Join the waitlist to be first to trade TM Global 100.

Why Rules-Based Crypto Indexing Matters in October 2025

In a volatile cycle, emotion creeps in: chasing winners late, cutting losers early, or missing re-entry after fear. Rules-based crypto indexing applies consistent criteria—constituent selection, weighting, and rebalancing—so you don’t have to improvise in stress.

For readers comparing crypto index options, think of it as a codified playbook. A rules-based crypto index is a methodology-driven basket that follows predefined signals (e.g., market regime) and maintenance schedules (e.g., weekly rebalancing), aiming for repeatable behavior across cycles.

Rules-based crypto indexing is a systematic approach that tracks a defined universe (e.g., top-100 by market cap) and maintains it on a fixed cadence, with explicit rules for when to hold tokens and when to de-risk into stablecoins.

How the TM Global 100 Index Works (Plain English)

  • Regime switching: When the market signal is bullish, the index holds the top 100 assets by market cap; when bearish, it moves to stablecoins until conditions improve.
  • Weekly rebalancing: Constituents and weights update weekly to reflect the latest market-cap rankings—capturing leadership changes without manual effort.
  • Transparency: A Strategy modal and Gauge → Treemap → Transactions Log show the signal, current mix, and every change recorded.

What you’ll see on launch: Price tile, “tokens: 100,” “rebalances weekly,” and a fast ~90-second Buy flow with fee/slippage previews.

See the strategy and rules. (TM Global 100 strategy)

Benefits at a Glance (Why This Beats DIY)

  • Time & operational drag: Skip juggling 20–100 tickers, wallets, and venues.
  • Execution quality: A single indexed flow can help reduce piecemeal slippage and duplicated fees.
  • No missed rotations: Weekly rebalancing and regime switching reduce the cost of being late to trends—or late to de-risk.
  • Always-on visibility: Holdings treemap + table + transactions log remove the black box.
  • Behavioral edge: Clear rules can limit panic sells and FOMO buys during turbulence.
  • Portfolio role: A disciplined core that you can complement with selective satellites.

Step-by-Step: How to Get Early Access (Waitlist)

  1. Open the Token Metrics Indices hub and select TM Global 100.
  2. Click Join Waitlist and enter your email for launch-day access.
  3. (Optional) Connect your wallet so you’re ready to fund.
  4. On launch, review the Gauge → Treemap → Transactions to confirm the current mix.
  5. Tap Buy Index, review fees/slippage, and confirm (about 90 seconds end-to-end).
  6. Track your position and every weekly rebalance in My Indices and the Transactions Log.

→ Join the waitlist to be first to trade TM Global 100.

Decision Guide: Is This Right for You?

  • Hands-Off Allocator: Want broad market beta with an explicit de-risking rule. Consider if you resist micromanaging.
  • Active Trader: Prefer a disciplined core that moves to stablecoins in bears while you express edge with satellites.
  • Long-Term Believer: Seek systematic participation in leadership changes via weekly rebalancing.
  • Transparency-First User: Require auditable holdings and a transactions log—no black boxes.
  • Tax/Compliance Conscious: Prefer consolidated rebalances over many ad hoc trades.
  • TM Research Follower: Want to pair TM insights with a rules-based execution layer.
  • New to Crypto Baskets: Want to avoid building and maintaining a DIY index.

FAQs

What is a rules-based crypto index?

A methodology-driven basket that follows predefined rules for asset selection, weighting, and maintenance. In TM Global 100, that means top-100 exposure in bullish regimes and stablecoins in bearish regimes, with weekly rebalancing and full transparency.

How often does the index rebalance?

Weekly. This cadence refreshes constituents and weights to align with current market-cap rankings; separate regime switches can move between tokens and stablecoins.

What triggers the move to stablecoins?

A documented market signal. When it turns bearish, the index exits to stablecoins; when bullish resumes, it re-enters the top-100 basket.

Can I fund with USDC or fiat?

Funding options will surface based on your connected wallet and supported rails. USDC settlement on sells is supported; fiat on-ramps may be added over time.

Is the wallet custodial?

No. The embedded wallet is self-custodial—you control your keys and assets.

How are fees shown?

Before confirming a trade, you’ll see estimated gas, platform fee, max slippage, and min expected value—so you can proceed with clarity.

How do I join the waitlist?

Go to the Indices hub, open TM Global 100, and enter your email. You’ll receive a launch-day link to buy.

Security, Risk & Transparency

  • Self-custody by default: You control your wallet.
  • Defense-in-depth: 2FA/account security features and explicit transaction prompts.
  • Clear economics: Fee and slippage previews before you confirm.
  • Auditability: Holdings treemap + table + transactions log document every change.
  • Methodology limits: Regime logic may not capture every market nuance; weekly cadence can differ from intraday moves.
  • Regional availability: On-ramps and features can vary by jurisdiction.

Crypto is volatile and can lose value. Past performance is not indicative of future results. This article is for research/education, not financial advice.

After a volatile cycle, the edge is process. Token Metrics Global 100 combines rules-based crypto indexing, weekly rebalancing, and full transparency so you can participate in upside and step aside during bears—without running your own spreadsheets. If that’s the core you’ve been missing, join the waitlist now.

Choose from Platinum, Gold, and Silver packages
Reach with 25–30% open rates and 0.5–1% CTR
Craft your own custom ad—from banners to tailored copy
Perfect for Crypto Exchanges, SaaS Tools, DeFi, and AI Products