Read a message

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety basics are covered. The description adds genuinely new context beyond the annotations: body format normalization (HTML to plain text) and an explicit prompt-injection warning that the text is data, not instructions. It does not mention truncation behavior, which is the one notable gap.

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 dense sentences with zero filler, front-loaded with the retrieval scope and ending on the highest-risk detail (untrusted content). Every clause carries information.

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?

An output schema exists, so return values need not be re-explained, and the annotations cover the safety profile. The description adequately covers content and format plus injection risk; the only shortfall is that truncation via max_chars is not surfaced for a tool that returns potentially large bodies.

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 only 67% and the description says nothing about any parameter. max_chars (truncation of the body) and include_quoted (quoted-reply handling) are explained only in the schema, and message_id has no description anywhere, so the agent gets no guidance on its expected format or the effect of truncation on the returned content.

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+resource ('One message in full') and enumerates exactly what is returned: sender, recipients, time, attachment names, and body text. This clearly separates it from search_messages or list_senders, though it never explicitly names the closest sibling get_thread.

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 by the phrase 'One message in full', which suggests single-message retrieval rather than thread or search retrieval. There is no explicit when-to-use statement, no mention of when to prefer get_thread, and no prerequisites called out.

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