> ## Documentation Index > Fetch the complete documentation index at: https://developers.telnyx.com/llms.txt > Use this file to discover all available pages before exploring further. # Issue a bot challenge > Generates a reverse-CAPTCHA challenge used to gate the bot signup flow. A random active problem is selected from the pool; math problems are returned obfuscated (case randomization, symbol injection, spacing noise) with an unobfuscated rounding instruction appended, while string and binary problems are returned as-is. The response contains a single-use nonce, the problem text, and the current terms-and-conditions and privacy-policy URLs, which must be echoed back on the signup request. Challenges expire after a short window (10 minutes by default) and can only be answered once. This endpoint is public and unauthenticated. ## OpenAPI ````yaml /openapi/source/external/signup/bot-signup.json post /v2/bot_challenge openapi: 3.0.0 info: version: 1.0.0 title: Bot Signup API contact: email: mission.control.squad@telnyx.com servers: - url: https://api.telnyx.com security: [] tags: - name: Bot Signup description: >- Agentic (bot) signup for Telnyx accounts. An AI agent solves a reverse-CAPTCHA challenge designed to be easy for LLMs and hard for humans, registers an account, and signs in by consuming a magic link emailed to the account owner. All endpoints are public and unauthenticated; signup endpoints are additionally gated by the freemium feature flags and per-country availability. paths: /v2/bot_challenge: post: tags: - Bot Signup summary: Issue a bot challenge description: >- Generates a reverse-CAPTCHA challenge used to gate the bot signup flow. A random active problem is selected from the pool; math problems are returned obfuscated (case randomization, symbol injection, spacing noise) with an unobfuscated rounding instruction appended, while string and binary problems are returned as-is. The response contains a single-use nonce, the problem text, and the current terms-and-conditions and privacy-policy URLs, which must be echoed back on the signup request. Challenges expire after a short window (10 minutes by default) and can only be answered once. This endpoint is public and unauthenticated. operationId: createBotChallenge requestBody: required: false description: >- Optional self-reported metadata about the LLM solving the challenge. Used for analytics only; it does not influence which problem is served. content: application/json: schema: $ref: '#/components/schemas/BotChallengeRequest' example: llm_model_name: claude-opus-4 llm_parameter_count: 175B llm_quantization: int8 responses: '201': description: Challenge issued. content: application/json: schema: $ref: '#/components/schemas/BotChallengeResponse' example: data: nonce: c6feda4e-6501-4db9-a21f-665e5b4ce2ba problem: >- W#hAt iS f!Ve tImEs sEvEn? Round to 0 decimal places. Omit units. challenge_type: math precision: 0 terms_and_conditions_url: https://telnyx.com/terms-and-conditions-of-service privacy_policy_url: https://telnyx.com/privacy-policy '400': description: The JSON request body could not be parsed. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: errors: - detail: >- There was a problem in the JSON you submitted. Please check your formatting and try again. '503': description: No bot challenge problems are currently available. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: errors: - detail: No bot challenge problems available security: [] components: schemas: BotChallengeRequest: type: object description: >- Optional self-reported metadata about the LLM solving the challenge. Analytics only; values are truncated to 50 characters. properties: llm_model_name: type: string description: Name of the LLM the client is using. example: claude-opus-4 llm_parameter_count: type: string description: Parameter count of the client LLM. example: 175B llm_quantization: type: string description: Quantization of the client LLM. example: int8 BotChallengeResponse: type: object required: - data properties: data: type: object required: - nonce - problem - challenge_type - terms_and_conditions_url - privacy_policy_url properties: nonce: type: string format: uuid description: >- Single-use challenge identifier. Submit it as `bot_challenge_nonce` on the signup request. example: c6feda4e-6501-4db9-a21f-665e5b4ce2ba problem: type: string description: >- Problem text to solve. Math problems are obfuscated and end with an unobfuscated rounding instruction; string and binary problems are returned as-is. example: >- W#hAt iS f!Ve tImEs sEvEn? Round to 0 decimal places. Omit units. challenge_type: type: string description: Type of challenge. enum: - math - string - binary example: math precision: type: integer description: >- Decimal places expected in the answer. Present only for math challenges. example: 0 terms_and_conditions_url: type: string description: >- Current terms-and-conditions URL. Echo this back on the signup request. example: https://telnyx.com/terms-and-conditions-of-service privacy_policy_url: type: string description: >- Current privacy-policy URL. Echo this back on the signup request. example: https://telnyx.com/privacy-policy ErrorResponse: type: object properties: errors: type: array items: $ref: '#/components/schemas/Error' required: - errors Error: type: object description: >- API error. General errors carry only `detail`; structured errors also include `code`, `title`, `source`, and `meta`. properties: code: type: string description: Machine-readable Telnyx error code. example: '10005' title: type: string description: Short human-readable summary. example: Resource not found detail: type: string description: Human-readable explanation of the error. example: The requested resource or URL could not be found. source: type: object properties: pointer: type: string description: JSON pointer to the offending attribute. example: / meta: type: object properties: url: type: string description: Link to the error documentation. example: https://developers.telnyx.com/docs/overview/errors/10005 required: - detail ````