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

With no annotations, the description carries full responsibility for behavioral disclosure. It clearly states that the body is decoded, may be truncated if huge, and that attachment contents are never returned. These are non-obvious behaviors that could surprise users, making this disclosure valuable.

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?

The description is two sentences, front-loaded with the action and scope. Every clause adds value: what is parsed, what is truncated, and what is excluded. There is no redundancy or 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 two-parameter tool with no output schema and no annotations, the description provides a complete contract. It specifies what is returned (headers, decoded body, attachment metadata), the truncation behavior, and the explicit exclusion of attachment contents. This is sufficient for an agent to invoke the tool confidently.

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% for both parameters, with 'id' and 'path' already described in the input schema. The description adds no new parameter-level meaning beyond referencing 'from search_messages', which is already implied by the schema. Since the schema fully covers parameter semantics, the baseline 3 is appropriate.

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 uses a specific verb ('Fully parse') and identifies the exact resource ('one message by its id'). It also distinguishes itself from sibling tools by referencing search_messages as the source of the id, making it clear this tool retrieves individual message details.

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?

The description implies a workflow: get an id from search_messages, then use get_message for full parsing. It also sets a clear limitation ('Attachment contents are never returned'), which suggests not using this tool for attachment content. However, it does not explicitly name alternatives or state when not to use beyond the attachment caveat.

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