list_recent_messages

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint as safe. The description adds value by stating it uses cached headers only, never returns bodies or unsubscribe links, and hides sender email by default, all without contradicting annotations.

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?

The description is two sentences plus a bullet list, front-loaded with the main purpose. Every sentence adds necessary information without redundancy.

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 tool with 6 parameters and no output schema, the description covers many behavioral aspects (cached headers, hidden sender, no bodies) and includes the prerequisite. Missing details on pagination (limit/offset), sorting, and time filtering (since), but remains fairly complete given the context.

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 description must compensate. It mentions the include_sender_email flag and hints at account/folder filtering via results, but does not explain limit, since, offset, or folder semantics in detail. Some meaning added but insufficient for all 6 parameters.

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 clearly states the tool lists recently scanned messages using cached headers, specifies the prerequisite (scan_mailbox), and details what is included/excluded. This distinguishes it from siblings like search_messages and get_message_headers.

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 instructs to run scan_mailbox first, providing a clear prerequisite. However, it does not compare with alternatives like search_messages or when to use get_message_headers instead, missing explicit exclusions.

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