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

The description discloses the exact visual behavior (frame stops, blurs, darkens, text burned and bound) and the two audio modes with their timeline effects. It also specifies that text and subtitle are burned centred, and provides parameter ranges, going well beyond the minimal annotation hints (which only indicate non-read-only). No contradiction with annotations.

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

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

The description is long but every sentence adds value, covering scoping, visual effect, parameter ranges, and audio behavior. It front-loads the project scoping constraint and then logically walks through the effect and options, making it dense yet efficient.

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

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

Given 13 parameters, no output schema, and no annotation details beyond non-read-only, the description covers the return value (project identity), the primary effect, all relevant parameter semantics, and both audio modes. It leaves little ambiguity for an agent to invoke it correctly, making it remarkably complete for its complexity.

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

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

With only 8% schema description coverage, the description compensates by explaining at_output_s, duration_s, blur, darken, motion, text, subtitle, and audio_mode with concrete values and effects. It does not cover font, color, template, or accent_color in detail, but these are either enums or straightforward strings; the description adds significant meaning for the most impactful parameters.

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

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

The description clearly states a specific verb and resource: it freezes a frame, holds it, and optionally adds text. It distinguishes itself from other add_* tools by describing the unique 'pearl' move with blur, darken, and motion effects on the held frame, making its purpose unambiguous.

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

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

It gives explicit guidance on when to use each audio_mode: 'pause' for a real cut that shifts subsequent content, and 'continue' to hold the visual while audio continues. It also recommends duration_s 2-4s and provides typical blur/darken values, effectively telling the agent how to invoke it appropriately.

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