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

Annotations already declare readOnlyHint=false, idempotentHint=false, and openWorldHint=true, so the mutating, non-repeatable nature is partly structured data. The description adds real value beyond that with '(free)' cost disclosure and the irreversibility implication of 'cannot be reused', but it omits what a second call returns and what error surfaces on a mismatch.

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 compact sentences with the effect front-loaded and the parameter caveat second; no filler. The bracketed host note is appropriately trailing. It is close to the minimum length that still conveys the key constraint.

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 five-parameter mutation tool with 0% schema coverage and no output schema, the definition covers the essential precondition and matching rule but leaves return behavior, failure modes, and the agentToken requirement unexplained. It is adequate to attempt a correct call but not complete.

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 five parameters, so the description must compensate and only partly does: it explains that amountUsd/host/payTo are optional and must match the approval, which is meaningful constraint information. The required id and agentToken parameters receive no explanation at all, leaving auth and identifier semantics 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?

The description states a specific verb and effect: mark the approval used so it cannot be reused. That clearly distinguishes it from approval_status (read) and approval_request (create), though it never explicitly names the nearest alternatives such as approval_cancel.

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?

'After paying' establishes the lifecycle moment for calling this tool, which is genuine usage context. However, there is no explicit guidance on when not to call it, what to do instead if the approval should be revoked (approval_cancel), or what an agent should do if the payment step failed.

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