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

Adds real context beyond the annotations: the secret is returned once only, must be stored, and is used as an 'Authorization: Bearer' token — critical for an agent handling a secret. The non-idempotent annotation is not elaborated, so it is unclear what a second claim with the same session_id returns (error vs. same key).

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?

Two sentences, no filler, front-loaded with the trigger condition followed by the security-critical handling instruction. Every clause adds information an agent needs.

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, the description still conveys that the return value is the API key itself and that it is unrecoverable afterward. Minor gaps remain around error/repeat-claim behavior and any auth requirements for calling it before a key exists.

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 coverage is 0%, so the description must carry the parameter burden, and it does: session_id is identified as the checkout session and its 'cs_' prefix is given as a recognizable format. It does not say where the agent obtains the session_id (which field of the buy_credits response).

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?

Specific verb+resource ('claim the new API key') plus the exact triggering condition ('after paying a buy_credits checkout without a key'), which distinguishes it from the sibling buy_credits call it depends on. An agent can tell what this does and where it sits in the flow without opening the 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?

Explicitly states the precondition (a completed buy_credits checkout that generated no key) and names the sibling that creates that state, so the ordering is unambiguous. It stops short of stating when NOT to call it, e.g. what to do if a key already exists or how to recover a lost key.

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