Fetch a message

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds the constraint that ids originate from search (implying failure on foreign ids), but it says nothing about whether attachments or headers are included, error behavior, or payload size limits.

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?

One front-loaded sentence that leads with the return value and then supplies the id form. Slightly redundant with the schema's own parameter description, but there is 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?

For a single-parameter read tool with full schema coverage and safety annotations, most of what an agent needs is present. With no output schema, however, the description is the only source describing the return value, and "full text" leaves open whether headers, metadata, or attachments are included.

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% and the single parameter's schema description is essentially identical to the note in the tool description. The description restates rather than extends the meaning, 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?

The description states the specific resource and result ("full text of a message returned by the search tool") and pins down the id format, so an agent knows this is a message-body retrieval by search result id. It does not distinguish itself from near-identical siblings such as read_email or read_thread, which is the main clarity gap.

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 through the precondition that the id must come from the search tool, which does usefully tell the agent it cannot pass arbitrary message ids. There is no explicit statement of when to pick this over read_email or search_emails, and no exclusions.

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