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

Beyond the annotations, the description adds genuinely important behavior: the subtitle source is consumed on call, re-execution is impossible, and there is no additional charge. This gives the agent critical expectations that structured fields alone do not convey.

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 short and front-loaded with the core action, and the consumption warning is clearly placed. The bilingual content is partially redundant, but it remains compact and scannable.

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?

For a single-parameter tool with destructive one-shot behavior, the description covers the essential completion requirement, the base64 return format, the consumption warning, and billing. No critical operational detail 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?

The input schema already documents job_id fully, including the 32-character format and the requirement that it be in completed state. The description adds no additional parameter-level meaning, so the baseline score is appropriate.

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 states a specific action ('Download the completed ASS subtitles') and a concrete resource (ASS subtitles as base64), making its purpose immediately clear. It is distinct from sibling tools like tts_jobs_status, tts_jobs_result, or tts_jobs_cancel, which have different resources or operations.

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?

The description clearly indicates the tool is for completed jobs and that the subtitle source is consumed on call, so it cannot be re-run. It does not explicitly name sibling alternatives, so it stops short of full when-to-use versus when-not-to-use guidance, but the usage context is clear.

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