reply_email

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

With no annotations provided, the description carries the full burden of disclosure. It clearly states the two operational modes (compose window vs. immediate send) and even warns that send=true acts 'without confirmation,' which is an important behavioral trait. It does not mention permissions or reversibility, but these are less critical for a compose/send action.

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 core purpose, and efficiently explains the send flag without wasted words. Every sentence earns its place.

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 tool is simple (3 params, no output schema), and the description covers the essential behavior and both send modes. It does not address potential sibling ambiguity (e.g., draft_reply), which would make it more complete, but otherwise it is sufficient for a task of this complexity.

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 description coverage is 100%, so the schema already documents all parameters thoroughly. The tool description adds nothing about message_ref or body beyond what's in the schema, and its explanation of send essentially repeats the schema. Baseline 3 is appropriate.

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 'Reply to an existing email,' which is a specific verb+resource that clearly states the tool's function. It also distinguishes from siblings like compose_email by focusing on replying to an existing message, and from draft_reply by describing the send behavior.

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 explains the send parameter's behavior, which gives context on how to invoke the tool. However, it does not explicitly mention when to prefer this over alternatives like draft_reply or compose_email, nor does it provide exclusion criteria. The guidance is implied rather than explicit.

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