Read an email

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely useful behavioral facts beyond that: HTML bodies are converted to text when no plain part exists, and attachment contents are never returned, which prevents an agent from promising file contents it cannot get.

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 tight sentences with no filler. The most decision-relevant fact for an agent (what comes back, and that attachment contents do not) is front-loaded in the first sentence, and the negative constraint is isolated in the second.

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 the job of describing the return payload: headers, body in text form, attachment names and sizes. It falls just short of complete by omitting any notion of body size limits, truncation, or failure modes for invalid ids on a tool flagged openWorldHint.

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% for the single message_id parameter, including a pattern and a note on where ids come from, so the schema carries the parameter burden. The description adds nothing further about the identifier format or what happens with a malformed or stale id, so the baseline 3 applies.

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?

"Read one email" states a specific verb and resource, and "one" distinguishes it from the sibling search_emails, which returns many. It doesn't explicitly name the siblings it competes with (get_thread, search_emails), so differentiation is implied rather than spelled out.

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 schema note "as returned by search_emails" suggests the read-after-search flow, and "one email" signals this is the single-message path rather than the thread or search path. There is no explicit when-to-use/when-not statement and no mention of error behavior for unknown ids.

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