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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds non-obvious behavior: chronological ordering (oldest first), quote stripping in snippets, and the exclusion of Drafts, Trash and Junk — real traits beyond the structured data.

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 dense sentences, front-loaded with what the tool returns, then identification, then the alternative. No filler; each clause 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?

An output schema exists so return details need not be repeated, yet the field summary usefully aids selection. Combined with the exclusion rules, identification methods, and routing to get_email, an agent has everything needed to call it correctly.

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 carries the burden, and it meaningfully explains the two identity params (mail_id from search_mail, or RFC Message-ID). The limit parameter (default 50) is never explained and slightly tensions with 'every message,' a minor gap.

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?

States a specific verb and resource (retrieve every message in one conversation) and enumerates the returned fields, so it's immediately clear what the tool produces. It explicitly distinguishes itself from get_email (full body) and mentions search_mail as the source of the identifier, separating it from siblings without needing to open a schema.

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?

Gives explicit routing ('Use get_email for a full body') and states the two ways to identify the target message (mail_id from search_mail, or RFC Message-ID). It lacks a general when-not condition against other read siblings like show_mail, but the alternative route is clearly stated.

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