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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered. The description adds genuine value beyond them by disclosing what each mode returns, including whether a vendor serves a newer version and per-mode pricing. It does not mention auth scope or rate limits, but nothing contradicts the 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?

One dense sentence with front-loaded default behavior followed by per-parameter modes; no wasted clauses. The telegraphic, parenthetical style ('vendor, endpoint, modes, what each makes') costs some readability but keeps it short.

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 need no explanation, and the three calling modes are all described. The remaining gap is the unmentioned 'kind' filter, which an agent would have to infer from the schema alone.

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%, so the description must carry parameter meaning. It explains own_model_id (single-model detail), search_vendor (catalog search) and q (the search term tied to search_vendor), but the 'kind' parameter with its image/video/audio enum is never mentioned, leaving one of four parameters undocumented anywhere.

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 ('the vendor models this account added to its own key') and enumerates the payload per mode (vendor, endpoint, modes, price). It is clearly distinguished from the generic list_models sibling by the 'own key' scoping and from add_own_model by naming that tool as the write counterpart.

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?

Each parameter is framed as a mode with its own purpose: bare call lists the account's models, own_model_id fetches one model plus version/price detail, search_vendor+q searches a catalog 'to find a model to add with add_own_model'. The routing to add_own_model is explicit, but there is no stated exclusion against the generic list_models tool, which an agent could confuse with the catalog-search mode.

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