> ## Documentation Index > Fetch the complete documentation index at: https://docs.anchorbrowser.io/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Anchor Browser provides cloud browsers for AI agents and automation: stealth browsing with residential proxies, managed authentication into third-party web apps, and browser sessions that run reliably at scale. AI agents that need Anchor credentials should start with https://docs.anchorbrowser.io/quickstart/agent-access. This flow lets agents obtain an API key programmatically without creating a dashboard account. Read that page before attempting authentication or API access. # Get Agent Access challenge > Get a puzzle and token. Follow next and challenge.prompt, then POST /v1/agent-access with token and answer. ## OpenAPI ````yaml /openapi.yaml get /v1/agent-access/challenge openapi: 3.1.0 info: title: AnchorBrowser API version: 1.0.0 description: > Anchor Browser ([anchorbrowser.io](https://anchorbrowser.io)) provides cloud browsers built for AI agents and automation. Use this API to launch and control browser sessions, run natural-language web tasks, authenticate into third-party web apps with managed identities, and capture recordings — reliably and at scale, without operating browser infrastructure yourself. ## Core resources - **Sessions** (`/v1/sessions`): launch configurable cloud browsers — residential proxies, stealth browsing, captcha solving, profiles, extensions, recording — and connect over CDP with Playwright, Puppeteer, or any CDP client. - **AI tools** (`/v1/tools/perform-web-task`): state a goal in natural language and the built-in agent completes it inside the browser. Related tools fetch webpages, take screenshots, render PDFs, and execute code in a session. - **Tasks** (`/v1/task`): create, version, deploy, and monitor repeatable browser automations built to run reliably in production. - **Applications and identities** (`/v1/applications`, `/v1/identities`): managed authentication into third-party web apps — including multi-step logins and TOTP-based 2FA — so agents can act on behalf of users. - **Profiles** (`/v1/profiles`): persist cookies and login state across sessions. - **OS-level control** (`/v1/sessions/{sessionId}/mouse`, `/keyboard`, `/clipboard`): raw input for flows that resist DOM automation. - Plus batch sessions for running browser fleets in parallel, session recordings, webhooks, events, extensions, client certificates, and billing usage. ## Authentication Pass an API key in the `anchor-api-key` header on every request. Create keys at [app.anchorbrowser.io](https://app.anchorbrowser.io) under API Access. AI agents that have no key yet can obtain one autonomously through the unauthenticated [agent-access flow](https://docs.anchorbrowser.io/quickstart/agent-access) (`POST /v1/agent-access`). ## For AI agents and LLMs - Docs: [docs.anchorbrowser.io](https://docs.anchorbrowser.io), with a machine-readable index at [/llms.txt](https://docs.anchorbrowser.io/llms.txt) and the full corpus at [/llms-full.txt](https://docs.anchorbrowser.io/llms-full.txt). - MCP server for hosted browser control: `https://api.anchorbrowser.io/mcp`. - Official SDKs: `anchorbrowser` on [npm](https://www.npmjs.com/package/anchorbrowser) and [PyPI](https://pypi.org/project/anchorbrowser/). `DELETE` operations terminate sessions or permanently remove resources (profiles, identities, extensions); `GET` operations are safe and read-only. servers: - url: https://api.anchorbrowser.io description: API server security: [] paths: /v1/agent-access/challenge: get: tags: - Agent Access summary: Get Agent Access challenge description: >- Get a puzzle and token. Follow next and challenge.prompt, then POST /v1/agent-access with token and answer. responses: '200': description: Challenge payload. content: application/json: schema: type: object required: - challenge - token - instructions properties: challenge: type: object required: - id - type - icon - title - description - prompt - timeLimit properties: id: type: string description: Challenge instance id. type: type: string description: Challenge type (semantic_logic). icon: type: string description: Display icon for UIs. title: type: string description: Short challenge title. description: type: string description: Short challenge summary. prompt: type: string description: >- Multi-step puzzle text. Follow the instructions to compute the final integer answer. timeLimit: type: number description: Suggested solve time in seconds. token: type: string description: >- Opaque challenge token. Pass to POST /v1/agent-access as token. This is not the puzzle answer. appendix_ref: type: string appendix_url: type: string instructions: $ref: '#/components/schemas/AgentAccessInstructions' next: $ref: '#/components/schemas/AgentAccessNextStep' '429': description: Too many challenge requests from this source. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Challenge generation failed. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' security: [] components: schemas: AgentAccessInstructions: type: object required: - submit - appendix - api_key_header - optional_identity - anonymous_credits - identity_credits properties: submit: type: string description: >- After solving the puzzle, call this endpoint with { token, answer }. token is from this response; answer is the final integer as a string. appendix: type: string description: Optional path hint from the challenge response. api_key_header: type: string description: >- After POST succeeds, send the returned api_key using this request header on authenticated API calls. optional_identity: type: string description: >- Optional identity_token on the same POST for more credits and an agent_identity_token for later calls. anonymous_credits: type: number description: >- Credits granted when POST omits identity_token or the token has no verified email. identity_credits: type: number description: >- Credits granted when POST includes identity_token with a verified email. AgentAccessNextStep: type: object required: - method - path - description properties: method: type: string enum: - GET - POST description: HTTP method for the next call in the Agent Access onboarding flow. path: type: string description: >- Path on https://api.anchorbrowser.io for the next call. Prepend the method to execute it. description: type: string description: >- Plain-language instruction for what to do on the next call and what you receive afterward. ErrorResponse: type: object properties: error: type: object properties: code: type: integer message: type: string ````