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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: message_id is an IMAP uid, not the Message-ID header, and it is folder-scoped — a real misuse trap an agent would otherwise fall into.

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?

Two sentences, front-loaded with what the tool does, followed by the identifier caveat. No filler. The second sentence concerns message_id, which is not a parameter of this tool, so it sits slightly outside the tool's immediate scope, but it is contractually useful.

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 does not describe the returned shape, but it implicitly signals that results carry a message_id usable downstream, and annotations cover the read-only/open-world profile. Adequate for an agent to call correctly, with the return format the only real gap.

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 100%, so the baseline would be 3. The description earns an extra point by clarifying what the 'query' parameter actually searches (From, Subject and body), which the schema only calls 'Text to search for'. It adds no detail for limit or folder, but those are fully specified in 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?

States a specific verb (search) and resource (connected email account messages) and specifies the searched fields (From, Subject, body). It is distinguishable from email_read and email_list_recent by describing query-based matching, though it never explicitly contrasts itself with those siblings.

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?

By noting that message_id comes 'from email_search or email_list_recent', it implies a workflow and hints these two are related entry points, but it never states when to prefer this tool over listing recent mail or reading a specific message. Usage is inferable rather than explicit.

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