hey_reply

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

Annotations declare this as a write operation (readOnlyHint=false) and not destructive, idempotent, or closed world. The description adds context about default behavior (excluding own address, preserving threading) and the effect of the 'to' parameter. This goes beyond annotations without contradicting them.

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 a single paragraph but well-structured, covering purpose, default behavior, when to use, and parameter guidance. It is concise without unnecessary fluff, though slightly long.

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 a reply action without output schema, the description covers essential aspects: default recipients, threading preservation, and parameter use. It provides enough context for an agent to use the tool 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?

Schema coverage is 100%, so baseline is 3. The description adds meaningful context to the 'to' parameter with concrete use cases, and explains default participant behavior, enhancing the schema descriptions.

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 starts with 'Reply to an email thread.' which clearly states the verb and resource. It distinguishes this tool from sibling 'hey_send_email' by explicitly stating when to prefer it ('Prefer this over hey_send_email any time you're responding to an existing thread').

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 explicit guidance on when to use this tool vs. 'hey_send_email'. It also gives specific scenarios for when to use the optional 'to' parameter, such as chasing own threads or redirecting away from a mailing-list address.

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