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

Annotations already declare readOnlyHint and idempotentHint, but the description adds behavioral nuance: it returns settings only, no mail, and lists the exact fields. This goes beyond the structured annotations, clarifying the scope of the read operation.

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 with no filler. The main action is front-loaded, followed by the return fields, a clarifying exclusion, and pointers to related tools. Every sentence earns its place.

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?

The description covers what the tool returns (settings fields), what it does not return (mail), how to find IDs, and where to go for messages and threads. With an output schema present and strong annotations, nothing essential is missing for correct invocation.

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?

Both parameters are fully documented in the schema (inbox_id and Authorization) with descriptions, so schema coverage is 100%. The description adds no additional parameter-level detail beyond referencing inbox_id in the action, which is redundant. Baseline of 3 is appropriate.

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 ('Fetches') and resource ('one inbox by inbox_id'), lists the returned fields, and explicitly distinguishes from sibling tools that handle messages and threads by naming them. It leaves no ambiguity about what this tool does.

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?

Provides explicit routing: 'For the messages in it use get_agentmail_inbox_messages, for conversations get_agentmail_inbox_threads. Discover ids with get_agentmail_inboxes.' This tells the agent exactly when to use this tool versus alternatives and how to find the required inbox_id.

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