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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is known. The description adds useful behavioral context beyond annotations: the tool fetches the full contents including the body, and approval cannot be performed from this tool. It does not introduce any contradictions.

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 sentences, each earning its place: the first establishes the operation and result, the second emphasizes read-only behavior, the third clarifies the boundary and points to the alternative. Highly concise and well-structured.

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?

Given the single documented parameter, the output schema, and the comprehensive annotations, the description provides everything an agent needs to call this tool correctly. It covers the purpose, the read-only nature, the approval limitation, and the source of approval_id.

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 100%, with the single parameter approval_id already described as returned by a gated send with status 'pending_approval'. The description does not add new parameter-level semantics, but it also does not need to because the schema carries the load.

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 uses the specific verb 'Fetch' and clearly identifies the resource: a send waiting for human approval, including its body. It also distinguishes itself from the approval action by stating 'Read-only' and 'Approving is not possible from here', which differentiates it from approval_decide and related siblings.

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?

The description explicitly states when to use the tool ('so it can be shown in the review card') and when not to use it ('Approving is not possible from here'). It even provides the alternative path: 'it requires the signed-in review page linked as review_url.' This gives clear routing guidance.

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