Read an email

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 does add real behavioral context beyond that: HTML is converted to text and the attachment list is metadata only. What it omits is the consequence of the 'try every connected account' fallback (possible latency, ambiguous match resolution), which is the one behavior an agent actually needs to reason about.

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 plus a routing clause, with the return payload front-loaded before the account caveat. Every clause carries information an agent would otherwise have to infer.

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 carries the return-shape burden and does so adequately by naming headers, labels, converted body, and attachment list. Truncation behavior is left entirely to the schema's maxBodyChars field, which is acceptable given full coverage there.

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 100%, so baseline is 3. The description does add routing value by saying the account should be the one shown in search results, but it conflicts slightly with the schema, which says omitting account uses the default while the description says every connected account is tried. That inconsistency costs it any credit above baseline.

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 one email') and then enumerates exactly what comes back: headers, labels, clean text body, and attachment list. It also distinguishes itself from adjacent readers by pointing attachment content lookups to read_attachment, so an agent can separate it from read_thread and read_attachment without opening 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 a concrete routing rule: use read_attachment for attachment contents, and pass the account value that appeared in search results. It does not address when to prefer read_thread over read_email for a message inside a conversation, which is the most plausible sibling ambiguity here.

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