Send an email

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

Adds important behavioral context beyond the annotations: the send is immediate and irreversible ('There is no undo'). This is a critical warning for a mutating side-effectful action. While it doesn't discuss failures or delivery semantics, the core risk is clearly disclosed.

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?

Every sentence earns its place: the action and immediacy are front-loaded, the no-undo warning is prominent, and the alternative tool is named concisely. No filler or redundant phrasing.

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?

For an 8-parameter mutating tool with no output schema, the description provides the necessary side-effect warning, user-intent safeguards, and routing guidance. Combined with the fully documented input schema, an agent has enough to invoke it correctly.

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?

The input schema already documents all 8 properties with meaningful descriptions, so the tool description adds little parameter-specific detail. Baseline 3 is appropriate because the schema carries the explanatory burden fully.

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?

Uses a specific verb and resource ('Compose and SEND a new email immediately') and clearly differentiates from create_draft by stating that sending happens now. The title and description align, and a sibling tool shares the email domain without ambiguity.

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 directs the agent to use create_draft when the user has not clearly asked for the message to be sent. This is a concrete conditional routing rule, which is ideal guidance for choosing between two otherwise similar sibling tools.

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