send_email

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

With no annotations provided, the description bears full responsibility for behavioral disclosure. It mentions that attachments require prior call to upload_attachment and that domain is inferred from inbox_id. However, it does not disclose what happens on failure, rate limits, authentication requirements, or how the output looks. Decent but incomplete.

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 moderately concise given 10 parameters. It starts with a clear one-liner, then breaks into explanatory notes and parameter definitions. Some redundancy exists (e.g., repeating 'optional'), but overall well-organized and front-loaded. Could be slightly tighter.

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?

Considering the tool's complexity (10 params, 2 required, no annotations, has output schema), the description covers key aspects: how to send with html/text, reply in thread, attach files, and parameter defaults. It omits error handling and return format, but the output schema likely covers the latter. Adequate for effective use.

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?

Input schema coverage is 0%, so the description must compensate. It provides detailed explanations for all 10 parameters in the Args section, including that 'to' accepts comma-separated values, 'attachments' expects IDs from upload_attachment, and 'inbox_id' triggers automatic domain inference. This adds significant meaning beyond the schema.

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 opens with 'Send an email message,' which clearly states the tool's purpose. It specifies the resource (email) and action (send). However, it does not explicitly distinguish this tool from sibling tools like send_sms or list_threads, though the context makes it generally clear.

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 provides clear usage guidance: it explains that inbox_id is sufficient for sending, that html or text can be provided, how to reply via thread_id, and how to attach files using upload_attachment. It does not mention when not to use this tool versus alternatives, but the guidance for execution is solid.

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