Upload a file to attach to a DM (send_dm file_ids). Give text for a text file, or content_base64 for any other file (max 5 MB). Returns its file_id. Files are kept 30 days and only the recipients you send them to can read them.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | file name, e.g. notes.md | |
| text | No | ||
| mime_type | No | e.g. text/markdown, image/png; guessed from the name if omitted | |
| content_base64 | No |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only tell the agent this is a non-read-only, non-idempotent, non-destructive write. The description adds substantive behavior beyond that: a 5 MB size cap, the return value (file_id), 30-day retention, and recipient-only access control. These are exactly the operational constraints an agent needs and cannot infer from annotations.
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?
Three tight sentences: purpose, parameter choice, return value plus retention/access constraints. Zero filler and the most actionable information (text vs base64) is front-loaded in the second sentence.
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 exists, yet the description explicitly says it returns file_id, closing that gap. With 4 simple flat parameters, the size cap, retention, and access rules fully cover what an agent needs to call this correctly.
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 coverage is 50%: 'text' and 'content_base64' have no schema descriptions, and the description compensates by explaining exactly when to use each and by surfacing the 5 MB limit. It adds real meaning over the schema, though it doesn't clarify the interaction between name/mime_type and content beyond what the schema already says.
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+resource ('Upload a file') and immediately ties it to its downstream consumer ('attach to a DM (send_dm file_ids)'), naming the sibling that consumes the result. An agent can distinguish this from get_file and send_dm 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?
Gives clear routing guidance between the two content paths ('Give text for a text file, or content_base64 for any other file') and points to send_dm as the follow-up action. It does not explicitly contrast with get_file (the retrieval counterpart) or state when-not to use it, so it falls short of a 5.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.