captapi

youtube_comment_replies

Replies under a top-level comment — parentReplyCount + cursor. Nested reply ids return 404. Costs 2 credits. Empty results and failures are never charged. Pass cache=true for a free 24h cache hit (default always fresh).

Input Schema

TableJSON Schema

Name	Required	Description
`url`	Yes	Public YouTube video URL, e.g. https://youtube.com/watch?v=ID. Not a TikTok/Instagram/Facebook URL. The URL platform must match this endpoint's platform. Do not pass cross-platform URLs, e.g. YouTube to TikTok, Instagram to Facebook, LinkedIn to X/Twitter, or Pinterest to Rumble.
`cache`	No	Set true to serve from the 24h response cache (0 credits on hit). Default false — always fetch fresh.
`limit`	No	Max items to return (default 50, max 500). Flat 2 credits per call.
`cursor`	No	Pagination cursor. Leave empty for the first page; then pass the nextCursor value returned in the previous response.
`commentId`	Yes	ID of the parent (top-level) comment to fetch replies for — from the comments endpoint. Legacy alias: comment_id.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 1, 2026

changedInput schema / properties / cache / description

Previous value: -"Set true to serve from the 24h response cache (0 credits on hit). Default false — always fetch fresh. Envelope includes cached + cachedAt on hits."New value: +"Set true to serve from the 24h response cache (0 credits on hit). Default false — always fetch fresh."

Changed4 schema fields changedAug 20, 2026

changedInput schema / properties / cache / description

Previous value: -"Set true to serve from the 24h response cache. Default false — always fetch fresh data."New value: +"Set true to serve from the 24h response cache (0 credits on hit). Default false — always fetch fresh. Envelope includes cached + cachedAt on hits."

changedInput schema / properties / commentId / description

Previous value: -"ID of the parent (top-level) comment to fetch replies for (from the comments endpoint). Legacy alias: comment_id."New value: +"ID of the parent (top-level) comment to fetch replies for — from the comments endpoint. Legacy alias: comment_id."

changedInput schema / properties / limit / description

Previous value: -"Max items to return. Default 50, max 500. Flat 2 credits per call."New value: +"Max items to return (default 50, max 500). Flat 2 credits per call."

changedInput schema / properties / url / description

Previous value: -"Public YouTube video URL, e.g. https://youtube.com/watch?v=ID. Not a TikTok/Instagram/Facebook URL. The URL platform must match this tool's platform. Do not pass cross-platform URLs, e.g. YouTube to TikTok, Instagram to Facebook, LinkedIn to X/Twitter, or Pinterest to Rumble."New value: +"Public YouTube video URL, e.g. https://youtube.com/watch?v=ID. Not a TikTok/Instagram/Facebook URL. The URL platform must match this endpoint's platform. Do not pass cross-platform URLs, e.g. YouTube to TikTok, Instagram to Facebook, LinkedIn to X/Twitter, or Pinterest to Rumble."

Changed5 schema fields changedAug 11, 2026

addedInput schema / properties / commentId

Added value: +{
+  "description": "ID of the parent (top-level) comment to fetch replies for (from the comments endpoint). Legacy alias: comment_id.",
+  "type": "string"
+}

removedInput schema / properties / comment_id

Removed value: -{
-  "description": "ID of the parent comment to fetch replies for (from the comments endpoint).",
-  "type": "string"
-}

addedInput schema / properties / cursor

Added value: +{
+  "description": "Pagination cursor. Leave empty for the first page; then pass the nextCursor value returned in the previous response.",
+  "type": "string"
+}

changedInput schema / properties / limit / description

Previous value: -"Max items to return. Default 50, max 500. Billed per result."New value: +"Max items to return. Default 50, max 500. Flat 2 credits per call."

changedInput schema / required

Previous value: -[
-  "url",
-  "comment_id"
-]New value: +[
+  "url",
+  "commentId"
+]

Changed1 schema field changedJul 16, 2026

changedInput schema / properties / cache / description

Previous value: -"Responses are cached for 24 hours by default. Set false to bypass the cache and always fetch fresh data (default true)."New value: +"Set true to serve from the 24h response cache. Default false — always fetch fresh data."

Changed1 schema field changedJul 15, 2026

addedInput schema / properties / cache

Added value: +{
+  "description": "Responses are cached for 24 hours by default. Set false to bypass the cache and always fetch fresh data (default true).",
+  "type": "boolean"
+}

Changed1 schema field changedJul 4, 2026

changedInput schema / properties / url / description

Previous value: -"Public YouTube video URL, e.g. https://youtube.com/watch?v=ID."New value: +"Public YouTube video URL, e.g. https://youtube.com/watch?v=ID. Not a TikTok/Instagram/Facebook URL. The URL platform must match this tool's platform. Do not pass cross-platform URLs, e.g. YouTube to TikTok, Instagram to Facebook, LinkedIn to X/Twitter, or Pinterest to Rumble."

First observedJun 7, 2026

TDQS

A4.4/5.0

Behavior5/5

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

No annotations exist, so the description carries full behavioral disclosure. It reveals the 2-credit cost, the no-charge guarantee for empty/failed calls, the cache behavior with cache=true, the pagination cursor pattern, and the 404 failure mode for nested IDs. This is unusually transparent.

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 dense and efficient, with every sentence carrying distinct value: scope, failure behavior, cost, cache, and freshness. The most decision-relevant information is front-loaded.

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

Completeness4/5

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

The description covers cost, caching, pagination, and failure behavior, which is strong for an endpoint with no output schema or annotations. A minor gap is that the response payload beyond parentReplyCount and cursor is not described, but the tool name and schema largely compensate.

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?

Schema description coverage is 100%, so the baseline is 3. The description reinforces cursor and cache semantics and mentions parentReplyCount, but it does not add meaningful parameter meaning beyond what the schema already documents.

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 names a precise resource ('Replies under a top-level comment') and a specific verb ('fetch'), making the tool's job unmistakable. It also differentiates from siblings by platform and by comment level, and the 'Nested reply ids return 404' line clarifies exactly which comments are acceptable.

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 clearly states the intended input is a top-level comment and warns against nested reply IDs. It does not explicitly name the sibling alternatives like youtube_comments or youtube_shorts_comments, but the scope is clear enough for an agent to route correctly.

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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youtube_comment_replies

Input Schema

Schema Changelog

TDQS

Glama MCP Gateway

Resources