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

With no annotations, the description carries the full burden and does well: it warns the key is shown only once, tells the agent to store it securely, and specifies the downstream Authorization: Bearer usage. Remaining gaps are re-claim behavior, expiry, and error semantics on an already-used session.

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 tight sentences with the precondition front-loaded and no filler. Every clause earns its place by adding an operational fact (source, format, one-time visibility, auth header).

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, no-output-schema tool, this covers the essential path: prerequisite, credential format, and what to do with the result. Missing only failure modes for expired or already-claimed sessions.

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 compensate, and it does: it identifies session_id as the checkout session identifier from buy_credits and even gives the 'cs_' prefix for format validation. It does not state whether the session id is reusable or single-use.

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 (claim) plus resource (the new API key), with the originating condition spelled out. It is clearly distinguishable from sibling buy_credits, which is the step that precedes it, rather than a competing tool.

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 trigger condition: after a buy_credits checkout that produced no key. That is a clear when-to-use with the alternative (buy_credits) named. It does not state when NOT to call it (e.g. if a key already exists or the session was already claimed).

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