Send one approved new outbound email

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

No annotations provided, so description carries full burden. Discloses approval requirement, auto-encoding of subjects, support for HTML format and legacy htmlBody, and threading behavior. Lacks details on error handling or rate limits but covers key traits for a send 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?

Single paragraph with clear logical flow: purpose, use case, requirements, encoding, body format, legacy support, safety warning. Front-loaded and no unnecessary words.

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?

Covers core aspects (purpose, key parameters, threading, approval) but misses details on less common parameters (cc, bcc, accountAlias, chatScope) and does not mention return value. For a 10-parameter tool with no output schema, description is moderately complete.

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 coverage is 0%, so description must compensate. Adds meaning for required parameters (to, subject), body/format/htmlBody, and threadId. Does not explain cc, bcc, accountAlias, or chatScope. Partial compensation but not comprehensive.

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 clearly states it sends a new email (not a reply) for campaigns and cold outreach, distinguishes from siblings by specifying 'no messageId' and mentioning threadId for chaining, which contrasts with a typical reply tool.

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?

Explicitly states when to use (campaigns, cold outreach) and when not to (explicit approval required). Gives context for threadId usage. Does not explicitly name sibling tools but implies when not to use via 'no messageId'.

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