search_messages

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 real behavioral value beyond that: all conditions are AND-ed, only headers are returned (not bodies), and results are ordered newest first. It omits pagination behavior, though limit's maximum suggests a cap.

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 short sentences, each carrying distinct information (scope, boolean semantics, return shape), with the core purpose front-loaded. No filler.

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?

With no output schema, the description usefully states the return shape (headers only, newest first). The remaining gap is pagination/windowing guidance given a 9-parameter search surface, but otherwise an agent has enough 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 78%, with per-parameter descriptions for the match fields and defaults on limit and mailbox, so the schema does most of the work. The description contributes the AND-combination rule, which is meaningful, but adds no matching semantics (exact vs substring) or date-format guidance beyond the schema.

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 gives a specific verb and resource ("Search messages in a mailbox") and scopes the operation. It does not explicitly differentiate itself from the sibling list_messages, so the agent must infer that "search" implies filtering while "list" does not.

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?

Usage is only implied: the mention of AND-combined conditions suggests this tool is for filtered queries, but there is no statement of when to prefer it over list_messages or get_message, and no stated prerequisites or exclusions.

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