ApiTap

The CLI, MCP server, and npm library that turns any website into an API — no docs, no SDK, no browser.

ApiTap is a CLI, MCP server, and npm library that lets AI agents (and you) browse the web through APIs instead of browsers. It ships with 6,400+ pre-mapped endpoints across 280+ APIs (Stripe, GitHub, Twilio, Slack, Spotify, and more) — ready to query on install. For sites not in the database, it captures API traffic from any website, generates reusable "skill files," and replays them directly with fetch(). No DOM, no selectors, no flaky waits. Token costs drop 20-100x compared to browser automation.

The web was built for human eyes; ApiTap makes it native to machines.

# Import 280+ APIs instantly — no browser needed
apitap import --from apis-guru --limit 100
  Done: 87 imported, 3 failed, 10 skipped
       1,847 endpoints added across 87 APIs

# Replay any imported endpoint immediately
apitap replay api.stripe.com get-listcharges limit=5

# Or capture a site's private API
apitap capture https://polymarket.com
apitap replay gamma-api.polymarket.com get-events

# Or read content directly
apitap read https://en.wikipedia.org/wiki/Node.js
  ✓ Wikipedia decoder: ~127 tokens (vs ~4,900 raw HTML)

No scraping. No browser. Just the API.

How It Works

ApiTap has three ways to build its API knowledge:

1. Import (instant) — Import OpenAPI/Swagger specs from the APIs.guru directory of 2,500+ public APIs, or from any spec URL/file. Endpoints get a confidence score based on spec quality. No browser needed.

2. Capture (30 seconds) — Launch a browser, visit a site, browse normally. ApiTap intercepts all network traffic via CDP, filters noise, and generates a skill file. Or use apitap attach to capture from your already-running Chrome.

3. Discover (automatic) — ApiTap auto-detects frameworks (WordPress, Next.js, Shopify) and probes for OpenAPI specs at common paths. Works without a browser.

All three paths produce the same artifact: a skill file — a portable JSON map of an API's endpoints, stored at ~/.apitap/skills/.

Import:   OpenAPI spec → Converter → Merge → skill.json (confidence 0.6-0.85)
Capture:  Browser → CDP listener → Filter → Skill Generator → skill.json (confidence 1.0)
Attach:   Running Chrome → CDP attach → Filter → skill.json (confidence 0.8-1.0)
Replay:   Agent → Replay Engine (skill.json) → fetch() → API → JSON response
                                                ↑ no browser in this path

Confidence Model

Every endpoint tracks how it was discovered:

Imported endpoints auto-upgrade to confidence 1.0 on first successful replay. The merge is additive — captured data is never overwritten by imports, imports fill gaps that capture missed.

Install

npm install -g @apitap/core

Claude Code — one command to wire it up:

claude mcp add -s user apitap -- apitap mcp

That's it. 12 MCP tools, ready to go. Requires Node.js 20+.

Note: npx @apitap/core mcp does not work due to npm scoped package bin resolution. Use npx apitap mcp or apitap-mcp instead.

Optional: To use capture and browse (which open a real browser), also run:

npx playwright install chromium

The read, peek, discover, and import tools work without it.

Quick Start

Import APIs instantly

# Import from the APIs.guru directory (2,500+ public APIs)
apitap import --from apis-guru --limit 100

# Import a specific API by name
apitap import --from apis-guru --search stripe

# Import a single OpenAPI spec from URL
apitap import https://api.apis.guru/v2/specs/stripe.com/2022-11-15/openapi.json

# Import a local spec file (JSON or YAML)
apitap import ./my-api-spec.json

# Skip auth-required APIs (open endpoints only)
apitap import --from apis-guru --limit 500 --no-auth-only

# Preview what would be imported
apitap import --from apis-guru --search twilio --dry-run

# Update previously imported APIs (skip unchanged)
apitap import --from apis-guru --update

Import produces a diff showing what changed:

Importing api.stripe.com from OpenAPI 3.0 spec...

  ✓ 12 existing captured endpoints preserved
  + 34 new endpoints added from OpenAPI spec
  ~ 8 endpoints enriched with spec metadata
  · 0 skipped (already imported)

  Skill file: ~/.apitap/skills/api.stripe.com.json (54 endpoints)

Captured endpoints are never overwritten. Import fills gaps and adds metadata (descriptions, response schemas, query param enums) from the spec.

Capture API traffic

# Capture from a single domain (default)
apitap capture https://polymarket.com

# Capture all domains (CDN, API subdomains, etc.)
apitap capture https://polymarket.com --all-domains

# Include response previews in the skill file
apitap capture https://polymarket.com --preview

# Stop after 30 seconds
apitap capture https://polymarket.com --duration 30

ApiTap opens a browser window. Browse the site normally — click around, scroll, search. Every API call is captured. Press Ctrl+C when done.

Attach to a running Chrome

# Launch Chrome with remote debugging enabled
google-chrome --remote-debugging-port=9222

# Attach to your signed-in Chrome — captures all tabs
apitap attach --port 9222

# Filter to specific domains
apitap attach --port 9222 --domain *.github.com

# Ctrl+C to stop — generates signed skill files for each captured domain

No separate browser, no re-login. Captures from your real Chrome sessions with all your cookies and auth tokens. When response bodies are evicted from Chrome's buffer (common on high-traffic pages), skeleton endpoints are written at confidence 0.8 instead of being dropped.

List and explore APIs

# List all skill files
apitap list
  ✓ api.stripe.com             446 endpoints   5m ago   [imported-signed]
  ✓ gamma-api.polymarket.com     3 endpoints   2h ago   [signed]
  ✓ api.github.com             499 endpoints   1h ago   [imported-signed]

# Show endpoints for a domain
apitap show api.stripe.com
  [ ] GET    /v1/account                    object (22 fields)
  [ ] GET    /v1/charges                    object (4 fields)
  [ ] GET    /v1/customers/:customer        object (30 fields)

# Search across all skill files
apitap search stripe

Replay an endpoint

# Replay with captured defaults
apitap replay gamma-api.polymarket.com get-events

# Override parameters
apitap replay gamma-api.polymarket.com get-events limit=5 offset=10

# Machine-readable JSON output
apitap replay gamma-api.polymarket.com get-events --json

Text-Mode Browsing

ApiTap includes a text-mode browsing pipeline — peek and read — that lets agents consume web content without launching a browser. Seven built-in decoders extract structured content from popular sites at a fraction of the token cost:

Average token savings: 74% across 83 tested domains.

# Triage first — zero-cost HEAD request
apitap peek https://reddit.com/r/programming
  ✓ accessible, recommendation: read

# Extract content — no browser needed
apitap read https://reddit.com/r/programming
  ✓ Reddit decoder: 12 posts, ~627 tokens

# Works for any URL — falls back to generic HTML extraction
apitap read https://example.com/blog/post

For MCP agents, apitap_peek and apitap_read are the fastest way to consume web content — use them before reaching for apitap_browse or apitap_capture.

Pre-Loaded APIs

ApiTap can instantly import from the APIs.guru directory of 2,500+ public API specs. A single command populates your local pattern database:

apitap import --from apis-guru --limit 500

Some of the APIs available out of the box:

Auth-required APIs import as endpoint maps with response schemas — you can explore what's available and see response shapes before setting up credentials. First successful replay with real auth auto-upgrades the endpoint to full captured status.

Why ApiTap?

Why not just use the public API? Most sites don't have one, or it's heavily rate-limited. The internal API that powers the SPA is often richer, faster, and already handles auth.

Why not just use Playwright/Puppeteer? Browser automation costs 50-200K tokens per page for an AI agent. ApiTap captures the API once, then your agent calls it directly at 1-5K tokens. No DOM, no selectors, no flaky waits.

Why not reverse-engineer the API manually? You could open DevTools and copy headers by hand. ApiTap does it in 30 seconds and gives you a portable file any agent can use.

Why not just use an OpenAPI spec? You can! apitap import converts OpenAPI/Swagger specs directly into skill files. But many sites don't publish specs — ApiTap captures their APIs from live traffic.

Isn't this just a MITM proxy? No. ApiTap is read-only — it uses Chrome DevTools Protocol to observe responses. No certificate setup, no request modification, no code injection.

Replayability Tiers

Every captured endpoint is classified by replay difficulty:

GET endpoints are auto-verified during capture by comparing Playwright responses with raw fetch() responses.

MCP Server

ApiTap includes an MCP server with 12 tools for Claude Desktop, Cursor, Windsurf, and other MCP-compatible clients.

# Start the MCP server
apitap mcp

# Also works via npx (no global install needed)
npx apitap mcp

The legacy apitap-mcp binary still works but apitap mcp is preferred. npx @apitap/core mcp does not work — npm can't resolve the default bin for scoped packages with multiple bins (#46).

Claude Code — see Install above.

Claude Desktop / Cursor / Windsurf — add to your MCP config:

{
  "mcpServers": {
    "apitap": {
      "command": "apitap",
      "args": ["mcp"]
    }
  }
}

VS Code (GitHub Copilot) — add .vscode/mcp.json:

{
  "servers": {
    "apitap": {
      "command": "apitap",
      "args": ["mcp"]
    }
  }
}

MCP Tools

You can also serve a single skill file as a dedicated MCP server with apitap serve <domain> — each endpoint becomes its own tool.

Chrome Extension

Optional. ApiTap works fully without the extension. Install it if you want passive API discovery or want to capture from your already-logged-in browser sessions.

The extension captures API traffic directly from your browser — no Playwright, no auth dance, no browser popups. It also silently builds a map of every API you visit in the background.

Why use the extension?

• You're already logged into Spotify, Discord, Reddit — the extension captures from your live session

• No apitap auth request needed — real tokens are captured automatically

• Passively builds a map of every API you visit, so your agents know what's available before asking

Setup

Step 1 — Install ApiTap CLI (if you haven't already):

npm install -g @apitap/core

Step 2 — Get the extension source:

git clone https://github.com/n1byn1kt/apitap.git
cd apitap

Step 3 — Build the extension:

cd extension && npm install && npm run build

Step 4 — Load into Chrome:

1. Open chrome://extensions

2. Enable Developer mode (toggle, top right)

3. Click Load unpacked

4. Select the extension/ folder inside the cloned repo

You should see the ApiTap icon appear in your toolbar.

Step 5 — Wire up native messaging (one-time):

apitap extension install --extension-id <your-extension-id>

Find your extension ID on the chrome://extensions page (shown under the extension name after loading).

Step 6 — Verify the connection:

Click the ApiTap icon in Chrome. The popup should show "CLI: Connected". If it shows disconnected, re-run Step 5 with the correct extension ID.

Passive Index (always-on)

Once installed, the extension silently observes API traffic as you browse — no infobar, no CDP, no performance impact. It builds a lightweight index of every domain's API shape: endpoints, HTTP methods, auth type, pagination patterns.

# See everything the extension has discovered
apitap index

# Filter to a specific domain
apitap index discord.com

The index lives at ~/.apitap/index.json and is automatically read by the apitap_discover MCP tool — so your agents can ask "what do you know about Discord's API?" and get a useful answer without triggering a full capture.

Promoting to a Full Skill File

The index is a map — it knows what endpoints exist but not their response shapes. To get a full replayable skill file, promote a domain:

From the popup: Click the ApiTap icon -> find the domain -> Generate skill file

Via agent: Your agent can request a capture automatically. You'll get a notification to approve, the extension briefly attaches CDP, captures response shapes, then detaches. The full skill file saves to ~/.apitap/skills/.

Auto-learn (opt-in): In the extension popup -> Settings -> enable Auto-learn. The extension will automatically promote domains you visit frequently. Off by default.

Manual Capture

For one-off captures without the passive index:

1. Click the ApiTap icon -> Start Capture

2. Browse the site — extension records API traffic

3. Click Stop -> skill file auto-saves to ~/.apitap/skills/

The popup shows CLI connection status and live capture stats. Auth tokens are encrypted with AES-256-GCM in session storage and automatically persisted to ~/.apitap/auth.enc via the native host, with [stored] placeholders in the exported skill files.

Note: Chrome Web Store submission coming soon. For now, load as an unpacked extension in Developer mode.

Auth Management

ApiTap automatically detects and stores auth credentials (Bearer tokens, API keys, cookies) during capture. Credentials are encrypted at rest with AES-256-GCM.

# View auth status
apitap auth api.example.com

# List all domains with stored auth
apitap auth --list

# Refresh expired tokens via browser
apitap refresh api.example.com

# Force fresh token before replay
apitap replay api.example.com get-data --fresh

# Clear stored auth
apitap auth api.example.com --clear

Skill Files

Skill files are JSON documents stored at ~/.apitap/skills/<domain>.json. They contain everything needed to replay an API — endpoints, headers, query params, request bodies, pagination patterns, and response shapes.

{
  "version": "1.2",
  "domain": "gamma-api.polymarket.com",
  "baseUrl": "https://gamma-api.polymarket.com",
  "endpoints": [
    {
      "id": "get-events",
      "method": "GET",
      "path": "/events",
      "queryParams": { "limit": { "type": "string", "example": "10" } },
      "headers": {},
      "responseShape": { "type": "object", "fields": ["id", "title", "slug"] },
      "confidence": 1.0,
      "endpointProvenance": "captured"
    }
  ]
}

Skill files are portable and shareable. Auth credentials are stored separately in encrypted storage — never in the skill file itself.

Import / Export

# Import a skill file from someone else
apitap import ./reddit-skills.json

# Import an OpenAPI spec (JSON or YAML)
apitap import ./stripe-openapi.json
apitap import https://api.apis.guru/v2/specs/stripe.com/2022-11-15/openapi.json

# Import validates: signature check / SSRF scan / format detection / confirmation

Imported files are re-signed with your local key. OpenAPI specs are automatically detected and converted using the same merge logic — captured endpoints are preserved, imports fill gaps.

Security

ApiTap handles untrusted skill files from the internet and replays HTTP requests on your behalf. That's a high-trust position, and we treat it seriously.

Defense in Depth

• Auth encryption — AES-256-GCM with PBKDF2 key derivation, keyed to your machine

• PII scrubbing — Emails, phones, IPs, credit cards, SSNs detected and redacted during capture

• SSRF protection — Multi-layer URL validation blocks access to internal networks (see below)

• Header injection protection — Allowlist prevents skill files from injecting dangerous HTTP headers (Host, X-Forwarded-For, Cookie, Authorization)

• Redirect validation — Manual redirect handling with SSRF re-check prevents redirect-to-internal-IP attacks

• DNS rebinding prevention — Resolved IPs are pinned to prevent TOCTOU attacks where DNS returns different IPs on second lookup

• Skill signing — HMAC-SHA256 signatures detect tampering; four-state provenance tracking (self/imported/imported-signed/unsigned)

• Atomic writes — Skill files are written to a temp file then renamed, preventing corruption from mid-write crashes

• Safe JSON parsing — Server responses parsed with safeParseJson() that returns raw text on malformed JSON instead of crashing

• Spec fetch hardening — OpenAPI spec imports are SSRF-validated, size-limited (10MB), timeout-limited (30s), and reject redirects

• External $ref rejection — Only local document #/ references are resolved; file:// and remote $ref pointers are blocked

• No phone-home — Everything runs locally. No external services, no telemetry

• Read-only capture — Playwright intercepts responses only. No request modification or code injection

Why SSRF Protection Matters

Since skill files can come from anywhere — shared by colleagues, downloaded from GitHub, or imported from untrusted sources — a malicious skill file is the primary threat vector. Here's what ApiTap defends against:

The attack: An attacker crafts a skill file with baseUrl: "http://169.254.169.254" (the AWS/cloud metadata endpoint) or baseUrl: "http://localhost:8080" (your internal services). When you replay an endpoint, your machine makes the request, potentially leaking cloud credentials or hitting internal APIs.

The defense: ApiTap validates every URL at multiple points:

Skill file imported
  -> validateUrl(): block private IPs, internal hostnames, non-HTTP schemes
  -> validateSkillFileUrls(): scan baseUrl + all endpoint example URLs

OpenAPI spec imported
  -> resolveAndValidateUrl(): SSRF check on spec URL before fetching
  -> resolveAndValidateUrl(): SSRF check on extracted API domain
  -> validateSkillFile(): validate merged skill file before writing

Endpoint replayed
  -> resolveAndValidateUrl(): DNS lookup + verify resolved IP isn't private
  -> IP pinning: fetch uses resolved IP directly (prevents DNS rebinding)
  -> Header filtering: strip dangerous headers from skill file
  -> Redirect check: if server redirects, validate new target before following

Blocked ranges: 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 (cloud metadata), 100.64.0.0/10 (CGNAT/Tailscale), 198.18.0.0/15 (benchmarking), 240.0.0.0/4 (reserved), 0.0.0.0, IPv6 equivalents (::1, fe80::/10, fc00::/7, ::ffff: mapped addresses), localhost, .local, .internal, file://, javascript: schemes. Alternative IP representations (decimal integer, octal, hex) are normalized before checking.

This is especially relevant now that MCP servers are being used as attack vectors in the wild — Google's Threat Intelligence Group recently documented underground toolkits built on compromised MCP servers. ApiTap is designed to be safe even when processing untrusted inputs.

Trap-Aware Mode

ApiTap ingests web content on behalf of agents, and adds inspection at the two places it already sits in the pipeline:

• apitap read scans raw HTML for hidden content containing explicit prompt-injection markers before extraction. Results are annotated on the response via a findings[] field; content is never modified.

• apitap replay optionally scans outbound request bodies and query strings for secret patterns (SSH keys, cloud credentials, API tokens) before the fetch() call. Opt-in per skill file or globally.

Read-side scanner

The read scanner runs by default on apitap read and the apitap_read MCP tool. It uses a two-condition gate: a finding is emitted only when content is in a hidden position (inline style:display:none, visibility:hidden, opacity:0, off-viewport positioning, hidden attribute, aria-hidden="true", or inside an HTML comment) and the hidden content matches an explicit role marker or a known prompt-injection signature.

Visible content never triggers a finding. Blog posts about prompt engineering, documentation of jailbreak techniques, and this README itself are all non-triggering.

Disable with --no-scan on the CLI or scan: false on the MCP tool.

apitap read https://example.com          # scan on by default
apitap read https://example.com --no-scan  # scan off

Known limitations:

• Class-based CSS hiding is not detected in v1.0. The generic HTML extractor strips <style> blocks before the scanner runs, so class-resolved hiding is invisible.

• Site-specific decoders (Reddit, YouTube, Wikipedia, HN, Twitter, Grokipedia, DeepWiki) bypass scanning. They extract from structured API sources rather than raw HTML.

• The scanner is a heuristic, not a classifier. Absence of findings is not proof of safety.

Egress-side scanner (opt-in)

The egress scanner is opt-in per domain or globally. Default behavior on upgrade is byte-identical to the previous release — cron-job users see zero change unless they explicitly enable it.

Three ways to enable:

Per skill file — add egress_check: true to the skill file (part of the signed payload):

{
  "version": "1.2",
  "domain": "api.example.com",
  "egress_check": true,
  "egress_action": "annotate",
  "endpoints": []
}

Globally — via $XDG_CONFIG_HOME/apitap/config.json:

{
  "egressCheckAll": true,
  "egressCheckAction": "annotate"
}

Per call — via the CLI flag or MCP tool argument:

apitap replay api.example.com post-submit --egress-check=annotate
apitap replay api.example.com post-submit --egress-check=block
apitap replay api.example.com post-submit --no-egress-check

Precedence: per-call → skill file → global config → off.

When enabled with annotate (default action), the request proceeds normally and the response envelope gains a warnings[] field. When enabled with block, high-severity findings refuse the request. medium-severity findings (PII) always annotate, never block.

Audit log

Both scanners write findings to $XDG_STATE_HOME/apitap/findings.jsonl (default: ~/.local/state/apitap/findings.jsonl):

apitap audit --findings
apitap audit --findings --source=egress --since=2026-04-01
apitap audit --findings --json

The audit log never contains matched secret bytes. Egress findings record pattern name, parameter location, structural path, and match length only.

Honest threat model

• The read scanner catches hidden content with explicit prompt-injection markers. It does not catch semantic manipulation, framing attacks, class-based hidden content, font-face remapping, or content hidden via external stylesheets.

• The egress scanner uses pattern matching. An attacker who can get the agent to encode or transform a secret before sending it will defeat pattern matching. This is defense in depth, not a DLP solution.

• The audit log is advisory tamper-evidence, same-user boundary. Same threat model as ApiTap's existing skill signing.

• v1.0 is rules-based. No learning loop. Tuning happens via signature list updates informed by audit log data.

CLI Reference

All commands support --json for machine-readable output.

Import flags

Capture flags

Development

git clone https://github.com/n1byn1kt/apitap.git
cd apitap
npm install
npm test          # ~1587 tests, Node built-in test runner
npm run typecheck # Type checking
npm run build     # Compile to dist/
npx tsx src/cli.ts capture <url>  # Run from source

Contact

Questions, feedback, or issues? -> hello@apitap.io

License

Business Source License 1.1 — free for all non-competing use (personal, internal, educational, research, open source). Cannot be rebranded and sold as a competing service. Converts to Apache 2.0 on February 7, 2029.