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WeftCut

WeftCut

by WeftCut
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TypeScript
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export_captions

Read-only

Export captions from all caption lanes or a single track as SRT or VTT subtitle documents, with optional range clipping and zero-shift alignment for range exports.

Instructions

The captions of a composition as a subtitle document — format srt or vtt — read from every caption lane (or one track_id) in time order, with the cue text as it stands. range (start_export's) clips cues to it and shifts them to 0, in step with a range export. Returns { format, cues, body }, plus the snapped range; write body to a file yourself. Records nothing.

Input Schema

NameRequiredDescriptionDefault
rangeNoSnapped to the frame grid as start_export snaps it; omit for all cues.
formatYesSubRip or WebVTT.
track_idNoOne caption lane only; omit for every caption lane of the composition.
composition_idNoComposition whose captions are meant — a Group's id from `project://compositions`; omit for the root.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.6.0
    • addedInput schema / properties / range
      Added value: +{
+  "additionalProperties": false,
+  "description": "Snapped to the frame grid as start_export snaps it; omit for all cues.",
+  "properties": {
+    "t_end_us": {
+      "description": "Exclusive end, timeline, µs.",
+      "type": "integer"
+    },
+    "t_start_us": {
+      "description": "Inclusive start, timeline, µs.",
+      "type": "integer"
+    }
+  },
+  "required": [
+    "t_start_us",
+    "t_end_us"
+  ],
+  "type": "object"
+}
  2. Addedv0.1.9

TDQS

A4.2/5.0
Behavior3/5

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

The annotations already establish readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds useful behavior beyond that: it discloses the return shape `{ format, cues, body }` plus the snapped `range`, states that the range is snapped to the frame grid like start_export, and notes 'Records nothing' and that no file is written. It does not cover error behavior or lane-ordering edge cases, so it sits at a solid but not exceptional level given annotation coverage.

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

Conciseness4/5

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

The description is front-loaded with the core action, then the range semantics, return shape, and the 'write body yourself' caveat. It is dense and telegraphic (heavy em-dash use), but essentially every clause carries information; minor tightening is possible but nothing is filler.

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?

With no output schema, the description compensates by specifying the returned object keys and the snapped range, and it covers all four parameters at 100% schema coverage. For a read-only export tool with nested range parameters, an agent has everything needed to call it and handle the result.

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

Parameters4/5

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

Schema coverage is 100%, so the schema baseline is 3; the description nonetheless adds real meaning by explaining that `range` clips cues and shifts them to 0 in step with a range export, and that `track_id` restricts to one lane while omission means all lanes. That is more than restating field names.

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 ('The captions of a composition as a subtitle document'), states the supported formats, and defines scope ('every caption lane (or one track_id) in time order'). That level of specificity clearly separates it from siblings such as merge_captions, apply_subtitles, and correct_caption_text.

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?

It gives clear context for when to use it: when you want cue text as it stands, aligned with a range export ('range (start_export's) ... in step with a range export'), and it tells the agent to write `body` to a file itself. It stops short of explicitly naming alternatives or stating exclusion conditions (for example, that this does not merge, apply, or correct captions).

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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