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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes further by disclosing both return shapes ({ok:true,...} vs {ok:false, errors[]}), the line-number error prefixing, and server-length rejection. That is substantive behavioral context beyond the annotations, though it omits any note on limits specifics or latency.

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 return-shape summary is well front-loaded, but the description then duplicates the entire multi-line script format block already present in the script parameter's schema description, which is significant redundancy for a definition of this size.

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?

With no output schema and 13 mostly-optional parameters, the definition compensates by spelling out success and failure return shapes and error formatting, and it covers the script grammar an agent must produce. Nothing essential for correct invocation is missing.

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?

Schema description coverage is 100%, so the schema already documents all 13 parameters, including defaults, enums, and ranges. The description repeats the script format and keyboard behavior verbatim rather than adding meaning beyond the schema, so the baseline 3 applies.

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?

States a specific verb (Checks/validates) and resource (a txtreel conversation, script or messages) and explicitly sets itself apart from rendering siblings with 'without rendering anything'. An agent can distinguish it from chat_render_video and chat_screenshot immediately.

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?

'without rendering anything' and 'It is fast and free' clearly establish the context for using this over the render/screenshot siblings, but it never explicitly says to validate before rendering or names the alternative. Clear usage context, no explicit exclusions.

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