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

Annotations cover safety (readOnly=false, destructive=false), and the description adds real behavioral context beyond them: the link expires in one hour, anyone holding it can upload, and the resulting file surfaces in list_uploads. That is valuable operational detail the annotations don't carry.

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?

One dense paragraph, front-loaded with what is returned, followed by invocation mechanics and the routing decision. Every clause carries information; nothing is padding.

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?

No output schema is needed because the description already explains the return value (a one-hour URL), how to consume it, and the side effect (file appears in list_uploads). For a one-parameter tool this is fully sufficient.

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 a single parameter and 100% schema description coverage, the schema already explains 'account' as the list_accounts id. The description adds no further parameter meaning, so the baseline of 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?

States a specific resource and outcome: returns a one-hour HTTPS upload link, where the file lands ("mailmcp-uploads"), and that it shows up in list_uploads. An agent can distinguish this from siblings like upload_attachment without opening either 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?

Gives an explicit conditional: upload it yourself if you can run commands, otherwise hand the link to the user. It doesn't name the alternative sibling (e.g. upload_attachment) explicitly, so the routing is clear but not tied to a named tool.

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