list_attachments

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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, and the description reinforces this with 'Read-only and local; nothing is downloaded.' It goes further by disclosing the empty-folder behavior and where attachments originate, which annotations cannot express.

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?

Front-loaded with the core action and scope, then return shape, then routing. Dense with semicolon-separated facts, but every clause carries information an agent needs; slightly long but not padded.

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?

With no output schema, the description supplies the return structure ({filename, path, size, modified}, sorted by filename, empty when the folder is missing), which is exactly what is needed. Nothing required to call it correctly is missing.

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?

Zero parameters, so the baseline is 4. The description still explicitly states 'No parameters,' removing any doubt about whether a path or filter argument exists.

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?

States a specific verb and resource (list attachment files) plus the exact scope (the local ~/Downloads/signal-attachments folder). It is clearly distinguishable from siblings get_attachment (details for one file) and send_attachment (uploading), which it references by name.

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?

Routes the agent explicitly: 'Pass a filename to get_attachment for its details,' and clarifies the relationship to receive_messages and the background service that populates the folder. It lacks an explicit when-not-to-use statement, but the context is unambiguous.

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