Send Message

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

Annotations already indicate destructiveHint=true (sending can have side effects), idempotentHint=true, and openWorldHint=true. The description adds only mention of optional features but no new behavioral context like authorization needs or rate limits. With annotations, the description's value is limited.

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 concise with two sentences. The first sentence states the action and optional features, and the second provides a critical usage condition. No wasted words, and it is front-loaded with the core purpose.

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?

Given the tool's complexity (18 parameters, nested objects, many optional fields) and the presence of annotations, the description is too brief. It does not explain return values, error handling, or relationships between parameters like staged attachments or idempotency key. Output schema exists but is not described.

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 only 17%, meaning few parameters are documented in the schema. The description mentions 'client correlation, scalar metadata, and validated safe headers' but does not explain specific parameters or their constraints, failing to compensate for the low schema coverage.

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 the tool sends an email from a mailbox ID, with optional features like client correlation and metadata. The verb 'Send' is explicit, and the resource (email from mailbox) is clear. While it doesn't explicitly distinguish from sibling reply or draft tools, the function is distinct enough.

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 a strong usage guideline: 'Use only after the user has explicitly asked to send or approved the exact recipients and content.' This clearly instructs the agent on when to use the tool, though it doesn't mention alternatives or when not to use it.

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