gmail_reply

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

No annotations are supplied, so the description carries the whole behavioral burden, and it discloses almost nothing: it does not say whether the reply is sent immediately or saved, whether it threads correctly, whether reply-all is supported, what permissions are needed, or what the call returns. For a mutation tool with zero annotation coverage this is a substantial gap.

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?

A single front-loaded sentence with no filler or redundancy. It is efficiently sized, though the brevity reflects under-specification rather than disciplined trimming.

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 genuinely simple – two required string parameters, full schema coverage, no nested objects – so the description is close to sufficient for correct invocation. What is missing is post-call behavior (return value, threading effect), which is not covered by an output schema or annotations.

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 both parameters (messageId, body, including HTML support) are already documented and the baseline of 3 applies. The description adds no syntax or format detail, and the 'thread' wording versus the messageId parameter leaves a small ambiguity about whether a thread ID would also work.

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 pairs a specific verb ('Reply') with a specific resource ('an existing email thread'), which cleanly distinguishes it from siblings like gmail_send, gmail_read, and gmail_search by name alone. It doesn't explicitly name those alternatives, but the action is unambiguous.

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?

There is no guidance on when to use this versus gmail_send for a new message, nor any stated prerequisites (must the thread exist, must the user be a participant, what happens if messageId belongs to a draft or a different account). The agent must infer the trigger conditions entirely.

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