send_email

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

With no annotations, the description carries the transparency burden. It discloses key behaviors: body supports html/text with fallback, attachments require a prerequisite upload, thread_id enables replying, and domain is auto-inferred from inbox_id. It lacks details on errors or permissions but provides meaningful context beyond a bare operation.

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 front-loaded with a one-line purpose, followed by brief usage notes and a structured Args list. Minor redundancy exists (e.g., thread_id and attachments are explained both in prose and Args), but the overall structure remains clear and easy to parse.

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?

The description covers the essential operational context for a 10-parameter tool: attachment ordering, threading, html/text alternatives, and inbox/domain resolution. It does not mention error handling or authorization, but the output schema exists and the description equips an agent to invoke the tool correctly in the common paths.

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 has 0% description coverage, and the Args section fully compensates by explaining all 10 parameters with practical details: comma-separated recipients, copy fallback, optional senders, and the upload_attachment dependency. This is a strong compensation for the silent 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,' a specific verb+resource pair that clearly identifies the tool's function. It naturally differentiates from sibling tools like send_sms by specifying email, and the name itself reinforces the purpose.

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?

Provides practical guidance: html/text body options, reply via thread_id, attachment workflow requiring upload_attachment first, and inbox_id/domain inference. However, it does not explicitly state when to choose this over send_sms or mention exclusions, so it falls short of a 5.

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