Capslane

by io.github.Webba-Creative-Technologies

Get YouTube transcript

get_youtube_transcript

Retrieve captions or generate a transcript for a public YouTube video. Each submission consumes a transcript unit, including cache hits. Can create a generation job. For summaries, notes or timestamp citations, retrieve the transcript first; this tool does not summarize.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`url`	Yes	Public YouTube URL or 11-character video ID
`lang`	No	Preferred ISO language code
`mode`	No	Cache first in every mode. On a miss: native never generates; auto generates only after missing captions; generate requests audio transcription	auto
`text`	No	Plain text for an immediate response. Completed jobs return segments with offsets and durations in milliseconds
`waitForCompletion`	No	Wait up to twenty minutes for generation. Set false for interactive clients, then poll the returned jobId with get_transcript_status

Output Schema

TableJSON Schema

Name	Required	Description
`lang`	No
`error`	No
`jobId`	No
`cached`	No
`source`	No
`status`	No	Job state, never an HTTP status. Completed without content means the stored result is unavailable or expired.
`content`	No	Transcript itself. Check this before jobId; it can coexist with a completed job ID.
`progress`	No
`requestId`	No
`availableLangs`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 9, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": true,
+  "properties": {
+    "availableLangs": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "cached": {
+      "type": "boolean"
+    },
+    "content": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "items": {
+            "additionalProperties": false,
+            "properties": {
+              "duration": {
+                "description": "Duration in milliseconds",
+                "minimum": 0,
+                "type": "number"
+              },
+              "lang": {
+                "type": "string"
+              },
+              "offset": {
+                "description": "Start offset in milliseconds",
+                "minimum": 0,
+                "type": "number"
+              },
+              "text": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "text",
+              "offset",
+              "duration",
+              "lang"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        }
+      ],
+      "description": "Transcript itself. Check this before jobId; it can coexist with a completed job ID."
+    },
+    "error": {
+      "type": "string"
+    },
+    "jobId": {
+      "type": "string"
+    },
+    "lang": {
+      "type": "string"
+    },
+    "progress": {
+      "type": "number"
+    },
+    "requestId": {
+      "type": "string"
+    },
+    "source": {
+      "enum": [
+        "native",
+        "generated"
+      ],
+      "type": "string"
+    },
+    "status": {
+      "description": "Job state, never an HTTP status. Completed without content means the stored result is unavailable or expired.",
+      "enum": [
+        "queued",
+        "downloading",
+        "processing",
+        "persisting",
+        "completed",
+        "failed",
+        "cancelled"
+      ],
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedSep 9, 2026

TDQS

A4.5/5.0

Behavior5/5

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

The description discloses non-obvious behaviors beyond the annotations: 'Each submission consumes a transcript unit, including cache hits' and 'Can create a generation job.' These additions clarify side effects (cost, background jobs) that the annotations (readOnlyHint=false, idempotentHint=false) only imply. This is valuable transparency.

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 three sentences with no fluff. It front-loads the core purpose, then discloses the side-effect cost, then gives usage guidance. Every sentence adds value and the structure is efficient.

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?

The description covers the essential context: purpose, public video requirement, unit consumption, job creation, and non-summarization. Combined with the detailed schema and annotations, an agent has everything needed to decide when and how to invoke it. The output schema exists to describe return structure, so no additional explanation is required.

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?

The input schema provides 100% parameter coverage with detailed descriptions (e.g., mode explains caching and generation behavior, waitForCompletion explains polling). The description itself adds minimal parameter-specific information beyond the schema, so it does not significantly improve on the schema's already rich semantics.

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 clearly states the tool's purpose: 'Retrieve captions or generate a transcript for a public YouTube video.' It uses a specific verb ('retrieve'/'generate') and resource ('transcript'), and differentiates itself from sibling tools by noting 'this tool does not summarize' and implying that it returns raw transcript for further processing. This distinguishes it from list_available_languages and get_transcript_status.

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 gives clear context on when to use the tool ('For summaries, notes or timestamp citations, retrieve the transcript first') and provides an exclusion ('this tool does not summarize'). However, it does not explicitly name alternative sibling tools or state when to prefer them, so the guidance is clear but not exhaustive.

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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