discord_get_message_attachments

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

Goes well beyond the readOnlyHint annotation by stating the required permissions (View Channel and Read Message History) and disclosing the non-obvious CDN behavior: urls carry a 24-hour signed expiry and are not re-signed on fetch, so cached urls can go stale. That expiry caveat is exactly the kind of operational trait an agent cannot infer from structured fields.

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?

Purpose is front-loaded and the permission/expiry caveats are short and high-value. The one weak spot is the long run-on enumeration of return fields (id, filename, title, url, proxyUrl, contentType, ...), which largely restates the output schema rather than adding information.

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 two-parameter read tool with an output schema and readOnly annotation, the description covers purpose, permissions, sibling routing, and the one genuinely surprising behavior (url expiry). Nothing an agent needs to call or interpret this 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?

Schema description coverage is 100%, so both channel_id and message_id are already documented, including snowflake patterns and the channel-or-thread ambiguity. The description adds no further meaning about these parameters, so the baseline 3 applies.

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?

Opens with a specific verb+resource ('List the file attachments of a message'), which is unambiguous and distinct from siblings like discord_read_messages or discord_fetch_pinned_messages. An agent can identify the correct tool without opening any schema.

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?

Explicitly routes the agent to discord_read_messages to find messages with attachments, and gives a concrete re-invocation rule ('re-call this tool if a stored url has expired'). It lacks a 'when not to use' clause, but the positive routing is clear enough.

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