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

Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds real value beyond that by disclosing the auth model (bearer capability only, no session fallback) and the sensitivity constraint (do not log or share the token), plus that the stored response is durable.

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?

Three tight sentences with the core action front-loaded and the security warning placed last. No filler, though the final sensitivity note is partly redundant with the schema's description of the token.

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?

It covers the trigger, auth model, and sensitivity for a three-parameter read tool with no output schema. It falls short on parameter meaning and says nothing about what the recovered response contains or how errors (e.g., invalid or expired capability) are surfaced.

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 only 33%, and only purchase_access_token carries a schema description. The description does not explain what api_id or buyer_wallet mean or why the wallet must be supplied alongside the capability, so the two undocumented parameters are left ambiguous in both places.

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 gives a specific verb and resource ("retrieve the exact durable response for one paid purchase") and scopes it to purchases made via paid execution. It distinguishes this from a session-based retrieval path, though it never names the sibling tools that could be confused with it.

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 states the prerequisite (the purchase capability returned by paid execution) and the exclusion (never falls back to a browser session), which implies when to use it. However, it gives no explicit guidance on when an agent should call this versus execute_api_call or get_api.

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