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

The annotations declare readOnlyHint=true, but the description describes write-like behavior: it says the tool will 'persist it as a chat attachment' and that non-parseable types are 'saved to the user's library'. This directly contradicts the read-only annotation, so the description does not align with the structured metadata.

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 well-structured, front-loads the core behavior, and every sentence earns its place. It covers use cases, supported file types, the alternative tool, parameter provenance, and return value shape without unnecessary 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?

Even though there is no output schema, the description specifies the return dict keys and how to continue with read_attachment. It also enumerates parseable types and gives fallback guidance, making the tool fully actionable for an agent.

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 the baseline is 3. The description adds a note that users should provide email_data_id and attachment_id from search_emails results, which mostly reinforces what the schema already says rather than adding substantial new meaning.

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 a specific action: fetch an email attachment, persist it as a chat attachment, and return a handle. It clearly distinguishes this from get_email_attachment and read_attachment by naming them and explaining what each is for.

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?

It explicitly says when to use this tool: to read attached documents such as spreadsheets or PDFs. It also gives a clear exclusion rule for non-parseable types and directs users to get_email_attachment when only fetching or transferring the file is needed.

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