reply_email

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

Annotations indicate readOnlyHint=false and destructiveHint=false, so the write nature is known. The description adds the behavioral detail of setting In-Reply-To and References headers, which is useful beyond annotations. However, it does not disclose other potential behaviors like authentication requirements or rate limits. This is adequate but not highly transparent.

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 two sentences, front-loaded with the action and key purpose, and contains no filler. Every word contributes to understanding the tool's function and prerequisite.

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 no output schema, the description provides the essential context: what the tool does, the threading behavior, and the prerequisite to read the original email first. Combined with comprehensive parameter descriptions in the schema and non-destructive annotations, this is sufficiently complete for an agent to invoke the tool. It could add success/failure expectations but is not critical for a straightforward reply action.

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 has 100% description coverage for all 7 parameters, so the description does not need to explain individual parameters. It adds no extra meaning beyond the schema, and the baseline for high schema coverage is 3. The prerequisite mention of get_email relates to emailId but is already covered in 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 clearly states the tool's purpose: 'Reply to an email with proper threading (In-Reply-To & References headers).' This uses a specific verb ('reply') and resource ('email') and adds a distinguishing technical detail (threading headers). It effectively differentiates from siblings like send_email and forward_email by focusing on replying to an existing email.

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 context by stating 'Use get_email first to read the original,' which is a prerequisite for correct use. It implies this tool is for replying to an existing email, but it does not explicitly exclude forwarding or sending new emails. This meets the standard of clear context without explicit alternatives.

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