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

With no annotations, the description carries the full burden, and it does disclose two non-obvious traits: the call is billed and the backend expects query parameters for this route. However, it says nothing about whether the operation is synchronous, whether it overwrites or creates a new subtitle, failure behavior for an invalid storage_path, or any permission requirements.

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?

Front-loaded with the core action, then constraints, then the SRT redirect — no filler. The line about the backend expecting query parameters is an internal implementation note that adds little for an agent and is the one sentence that does not fully earn its place.

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?

An output schema exists, so return values needn't be explained, and the critical routing and billing facts are present for a billed write-style tool. The remaining gap is that the non-required parameters (context, glossary) and the language-code convention are left entirely to an undocumented schema.

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 0% across four parameters, and the description only clarifies storage_path (its provenance and that a local path or URL is invalid). target_languages (language code format?), context, and glossary (what format a glossary string takes) get no explanation anywhere, leaving three of four parameters undocumented.

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 and resource with scope: localize an *already saved ITT subtitle file* via its storage path. It also names the sibling path for the SRT case (upload_subtitle(auto_localize=true) or localize_subtitles), so an agent can tell this apart from the other localization tools without opening a schema.

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?

Gives explicit routing: use this only for files already in storage, source storage_path from upload_subtitle/list_subtitles, and do not pass a local path or HTTPS URL. It also names the alternatives for SRT, which is exactly the when-not/alternative guidance an agent needs.

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