proofcut

Overview Schema Source Related Servers Discussions Admin

check_black

Read-onlyIdempotent

Scan a video render for black stretches, distinguishing known kdenlive tail frames from genuine defects. Requires a target render to analyze.

Instructions

Scan a render for black stretches, and say whether each is the known kdenlive-export tail frame (picture.KNOWN_TAIL_FRAME) or a genuine defect.

target is required — unlike check_frames, there is no cheap no-target mode; there is nothing to detect black in without a render. A run is only ever explained when it sits at the tail and the frame delta against the timeline matches the known defect exactly; a black run inside the declared picture is always reported as a real defect.

Input Schema

TableJSON Schema

Name	Required	Description
`fps`	No	The rate the timeline's own frame arithmetic is counted on.
`path`	No	The project directory to act on. Omit it — the usual case — when this server is bound to a project (started as `proofcut -C DIR mcp`, or inside a project; `ping` says which): it then resolves to that one bound project, a relative path resolves against it, and a path outside it is refused by name. Unbound, `path` is the whole address and omitting it refuses rather than guessing.
`pix_th`	No	How dark a pixel counts as black, 0–1.
`target`	Yes	The render to scan. Required — unlike `check_frames` there is no cheap no-target mode, since there is nothing to detect black in without a render.
`min_duration`	No	Shortest black run to report, in seconds.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed17 schema fields changedv0.25.0Sep 16, 2026

removedInput schema / properties / fps / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / fps / description

Added value: +"The rate the timeline's own frame arithmetic is counted on."

removedInput schema / properties / fps / title
```
Removed value: -"Fps"
```

addedInput schema / properties / fps / type

Added value: +[
+  "number",
+  "null"
+]

removedInput schema / properties / min_duration / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / min_duration / description

Added value: +"Shortest black run to report, in seconds."

removedInput schema / properties / min_duration / title
```
Removed value: -"Min Duration"
```
addedInput schema / properties / min_duration / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedInput schema / properties / path / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / path / description

Added value: +"The project directory to act on. Omit it — the usual case — when this server is bound to a project (started as `proofcut -C DIR mcp`, or inside a project; `ping` says which): it then resolves to that one bound project, a relative path resolves against it, and a path outside it is refused by name. Unbound, `path` is the whole address and omitting it refuses rather than guessing."

removedInput schema / properties / path / title
```
Removed value: -"Path"
```

addedInput schema / properties / path / type

Added value: +[
+  "string",
+  "null"
+]

addedInput schema / properties / pix_th / description

Added value: +"How dark a pixel counts as black, 0–1."

removedInput schema / properties / pix_th / title
```
Removed value: -"Pix Th"
```

addedInput schema / properties / target / description

Added value: +"The render to scan. Required — unlike `check_frames` there is no cheap no-target mode, since there is nothing to detect black in without a render."

removedInput schema / properties / target / title
```
Removed value: -"Target"
```
removedInput schema / title
```
Removed value: -"check_blackArguments"
```

First observedv0.24.0Sep 15, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Even though annotations already declare readOnly/idempotent/non-destructive, the description adds important behavioral detail: a run is only 'explained' as the known tail defect when it is at the tail AND the frame delta matches exactly; any black run inside the picture is always a real defect. This is substantive decision logic beyond what annotations reveal.

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: the core purpose appears in the first sentence, followed by the key usage constraint and the classification rule. Every sentence adds value and none are wasted.

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 annotations covering safety, an output schema present, and the input schema fully documented, the description supplies the remaining essential context: required target, the invariant classification logic, and the reference to check_frames. An agent has everything needed to decide when and how to call this tool correctly.

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 schema already documents every parameter. The description repeats the target-required rationale that already appears in the schema's target property, adding no meaning beyond that. Other parameters are left entirely to the schema, which is acceptable but not enhanced.

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: 'Scan a render for black stretches' and states the two possible verdicts (known kdenlive-export tail frame vs genuine defect). It distinguishes itself from sibling check_frames by name and by the absent no-target mode, so an agent can tell them apart without inspecting schemas.

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 explicitly says `target` is required and contrasts with check_frames' cheap no-target mode, giving a clear condition for using this tool. It does not enumerate broader when-to-use vs when-not-to-use scenarios, but the target requirement and the classification rule provide solid contextual guidance.

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

Deploy Server