Compose Message With File

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

The description discloses that the message is only sent or scheduled after user action, aligning with readOnlyHint=true. It adds context about the review card workflow, but could mention more about the async nature.

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?

Two short sentences with no filler. The first sentence captures the core action and prerequisites, the second gives an alternative. Every part serves a purpose.

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 description covers the behavioral workflow and alternative tool, but lacks parameter details for a complex 16-param tool with nested objects. Output schema exists but is not referenced. Adequate but not fully complete.

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?

With only 6% schema coverage, the description provides no additional meaning for the 16 parameters beyond mentioning file. The many email fields (cc, bcc, html, etc.) are left unexplained, which is insufficient for correct tool invocation.

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 opens a review card for a conversation or library file using MCP Apps file handoff. It distinguishes from the sibling tool shipmail_prepare_staged_attachment_upload by specifying 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?

The description explicitly states when to use this tool (for host-supported MCP Apps file handoff) and when not (for local filesystem paths, use the mentioned sibling). This provides clear guidance to the agent.

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