read_mail

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

With no annotations, the description carries the full burden and does disclose key traits: output is truncated, it returns headers and plain-text content, and it explicitly states it does not modify the mailbox. It omits auth requirements and behavior when no message matches, but the core behavioral profile is present.

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 core behavior and read-only guarantee are front-loaded, and the query guidance is compact and free of filler. Slightly more length could have been traded for documenting max_chars, but nothing is wasted.

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 two-parameter read tool with no annotations and no output schema, the description covers the essentials: matched-scope, truncation, returned content type, and non-mutation. The remaining gaps (max_chars semantics, empty-result behavior) are minor but real.

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%, so the description must compensate. It partially does for 'query' by explaining message-id syntax and combinable terms, but 'max_chars' is never mentioned, and the truncation note only indirectly implies its purpose. One of two parameters remains effectively 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?

States a specific verb and resource ('Read the first message matching a mu query') and clarifies the scope with 'first message' vs. a broader list. It does not explicitly contrast itself with the sibling search_mail, so sibling differentiation is left to inference.

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?

It advises using a specific query and gives effective query strategies ('message-id:abc@example.com' or combining sender, subject, date terms), which is useful invocation guidance. However, it never says when to choose read_mail over search_mail, so the tool-selection guidance is only implied.

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