Reply To Message

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

Annotations already indicate idempotentHint=true and openWorldHint=true. The description adds no additional behavioral traits beyond 'reply to a specific message', and does not disclose potential side effects or required permissions.

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 extremely brief (one sentence plus condition), which is concise but at the expense of necessary detail. Every sentence is functional, but more context could be added without being verbose.

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 the tool has 7 parameters, an output schema, and a sibling tool for replying to threads, the description is too minimal. It omits response format, behavior for multiple recipients, threading details, and how it differs from 'shipmail_reply_to_thread'.

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 tool description does not explain any parameters. Schema_description_coverage is only 29% (only idempotency_key described in schema). The description adds no meaning beyond parameter names, leaving ambiguity for complex fields like 'to' and 'cc'.

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 it replies to a specific message, but does not distinguish it from the sibling tool 'shipmail_reply_to_thread', which could cause confusion about when to use each.

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?

Provides a condition ('use only after the user approves the exact recipients and content') but lacks explicit guidance on when not to use, prerequisites, or alternatives.

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