get-fileDownload a sent or received fax file.
Side effects: none (read-only); returns base64 file bytes in structured output.
| Name | Required | Description | Default |
|---|---|---|---|
| fax_id | Yes | Fax record ID whose file should be downloaded. | |
| format | No | 'pdf' (default) or 'tiff'. | |
| user_id | No | Fax.Plus user ID. Default: self. |
| Name | Required | Description | Default |
|---|---|---|---|
| data_base64 | Yes | ||
| content_type | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description explicitly states 'Side effects: none (read-only)' and 'returns base64 file bytes in structured output', adding useful behavioral context beyond the annotations. It is consistent with the readOnlyHint, idempotentHint, and destructiveHint annotations, with no contradiction.
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?
The description is two short sentences with the primary action front-loaded and the side-effect/output note in a clearly separated second sentence. There is no filler or redundant content.
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?
Given the rich input schema, output schema, and safety annotations, the description is sufficient for an agent to invoke the tool correctly. It does not discuss alternatives like thumbnails or pages, but those are not required to make the call.
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%, with fax_id, format, and user_id all documented in the input schema. The description adds no parameter-specific meaning beyond what the schema already provides, so the baseline score of 3 is appropriate.
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 uses the specific verb 'Download' and identifies the resource as 'a sent or received fax file', which clearly states what the tool does. It does not explicitly name sibling tools like get-fax-thumbnail or get-file-page to differentiate them, but the full-file download meaning is clear.
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 provides no explicit guidance on when to use this tool versus alternatives such as get-fax-thumbnail or get-file-page. An agent must infer the appropriate use case from the tool name and sibling names, which is not enough guidance for a tool with several file-related siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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