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YouTube Transcript

youtube_transcript
Read-only

Fetch the transcript of a YouTube video (manual or auto-generated captions) as timestamped segments plus full text, with language preference and English fallback. Accepts a video id or any YouTube URL. No API key, no download. Pay per call with USDC or USDT on Base via x402. 3 free calls per wallet.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
walletNoYour EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet).
api_keyNoOptional AMR enterprise API key.
languageNoPreferred caption language (default en).en
video_idYes11-char video id or YouTube URL.
x_paymentNoOptional signed x402 payment payload (base64 JSON) for USDC/USDT on Base.
include_segmentsNoReturn timestamped segments (default true).

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
titleNo
tokenNoToken actually used for payment (USDC, USDT or FREE).USDC
routingYesHow the request was routed (provider, fallback, cache, latency).
languageYes
segmentsNo
video_idYes
cost_usdcYesPrice charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.
full_textYes
fetched_atNoUTC timestamp when the data was fetched.
word_countYes
is_generatedNo
segment_countYes
duration_secondsYes
freshness_secondsYesAge of the underlying data in seconds (0 = fetched live).
x_payment_responseNoBase64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "description": "Response for ``POST /youtube-transcript``.",
      +  "properties": {
      +    "cost_usdc": {
      +      "description": "Price charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.",
      +      "title": "Cost Usdc",
      +      "type": "number"
      +    },
      +    "duration_seconds": {
      +      "title": "Duration Seconds",
      +      "type": "integer"
      +    },
      +    "fetched_at": {
      +      "description": "UTC timestamp when the data was fetched.",
      +      "format": "date-time",
      +      "title": "Fetched At",
      +      "type": "string"
      +    },
      +    "freshness_seconds": {
      +      "description": "Age of the underlying data in seconds (0 = fetched live).",
      +      "title": "Freshness Seconds",
      +      "type": "integer"
      +    },
      +    "full_text": {
      +      "title": "Full Text",
      +      "type": "string"
      +    },
      +    "is_generated": {
      +      "default": false,
      +      "title": "Is Generated",
      +      "type": "boolean"
      +    },
      +    "language": {
      +      "title": "Language",
      +      "type": "string"
      +    },
      +    "routing": {
      +      "description": "How the request was routed (provider, fallback, cache, latency).",
      +      "properties": {
      +        "cache_hit": {
      +          "default": false,
      +          "description": "True if the result was served from cache.",
      +          "title": "Cache Hit",
      +          "type": "boolean"
      +        },
      +        "fallback_used": {
      +          "default": false,
      +          "description": "True if the primary provider failed and a fallback served the result.",
      +          "title": "Fallback Used",
      +          "type": "boolean"
      +        },
      +        "latency_ms": {
      +          "default": 0,
      +          "description": "End-to-end routing latency in milliseconds.",
      +          "title": "Latency Ms",
      +          "type": "integer"
      +        },
      +        "provider": {
      +          "description": "Name of the upstream provider that served the result.",
      +          "title": "Provider",
      +          "type": "string"
      +        },
      +        "providers_tried": {
      +          "description": "Providers attempted, in order.",
      +          "items": {
      +            "type": "string"
      +          },
      +          "title": "Providers Tried",
      +          "type": "array"
      +        }
      +      },
      +      "required": [
      +        "provider"
      +      ],
      +      "title": "RoutingMeta",
      +      "type": "object"
      +    },
      +    "segment_count": {
      +      "title": "Segment Count",
      +      "type": "integer"
      +    },
      +    "segments": {
      +      "items": {
      +        "properties": {
      +          "end": {
      +            "title": "End",
      +            "type": "number"
      +          },
      +          "start": {
      +            "title": "Start",
      +            "type": "number"
      +          },
      +          "text": {
      +            "title": "Text",
      +            "type": "string"
      +          }
      +        },
      +        "required": [
      +          "start",
      +          "end",
      +          "text"
      +        ],
      +        "title": "TranscriptSegment",
      +        "type": "object"
      +      },
      +      "title": "Segments",
      +      "type": "array"
      +    },
      +    "title": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ],
      +      "default": null,
      +      "title": "Title"
      +    },
      +    "token": {
      +      "default": "USDC",
      +      "description": "Token actually used for payment (USDC, USDT or FREE).",
      +      "title": "Token",
      +      "type": "string"
      +    },
      +    "video_id": {
      +      "title": "Video Id",
      +      "type": "string"
      +    },
      +    "word_count": {
      +      "title": "Word Count",
      +      "type": "integer"
      +    },
      +    "x_payment_response": {
      +      "description": "Base64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.",
      +      "type": "string"
      +    }
      +  },
      +  "required": [
      +    "freshness_seconds",
      +    "cost_usdc",
      +    "routing",
      +    "video_id",
      +    "language",
      +    "duration_seconds",
      +    "segment_count",
      +    "full_text",
      +    "word_count"
      +  ],
      +  "type": "object"
      +}
  2. Changed3 schema fields changed
    • addedInput schema / properties / include_segments / default
      Added value: +true
    • addedInput schema / properties / language / default
      Added value: +"en"
    • changedInput schema / properties / wallet / description
      Previous value: -"Your EVM wallet address (0x...). Unlocks the free tier (3 calls per wallet)."New value: +"Your EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet)."
  3. Added

TDQS

A4.5/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyound the readOnlyHint and openWorldHint annotations, the description explains key behavioral details: it supports manual or auto-generated captions, has an English fallback, requires no download, has no API key requirement, and is paid via x402 with 3 free calls per wallet. This gives an agent a realistic picture of what happens when the tool is invoked.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded: core function first, then accepted inputs, then access and payment terms. Every sentence contributes useful information without repeating schema details or padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with 6 parameters and no nested objects, the description covers the essential operational context: input format, caption sources, output type, language fallback, authentication/API-key status, and billing/free-tier mechanics. Since an output schema exists, explicit return-value documentation is unnecessary here.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Input schema coverage is 100%, so the schema already documents all parameters. The description adds some useful behavior context, like language preference and English fallback, but does not materially explain wallet, api_key, or x_payment beyond what the schema states. The phrase 'No API key' is slightly oversimplified given the optional api_key parameter, but the schema clarifies it is optional.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Fetch the transcript of a YouTube video'. It further clarifies the output ('timestamped segments plus full text') and scope ('manual or auto-generated captions'), making the tool's purpose unambiguous and differentiating it from the broad sibling list.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear usage context: accept a video id or any YouTube URL, no API key required, output is timestamped segments plus full text, and payment/ free-tier conditions. It does not explicitly state when not to use it or name alternatives, but given the sibling set and the explicit resource scope, an agent can determine when this tool applies.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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