Fax.Plus

Download fax file

get-file

Read-onlyIdempotent

Return a short-lived URL for a sent or received fax file (pdf or tiff). Save that URL to a file on disk immediately. Do not paste the file bytes into the conversation. Open the saved file when the user wants to view it.

Side effects: none (read-only); returns url and expiration_seconds, not file bytes.

Input Schema

Name	Required	Description	Default
`fax_id`	Yes	Fax record ID whose file should be downloaded.
`format`	No	'pdf' (default) or 'tiff'.	pdf
`user_id`	No	Fax.Plus user ID. Default: self.

Output Schema

Name	Required	Description	Default
`url`	Yes
`expiration_seconds`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 23, 2026

removedOutput schema / properties / content_type
```
Removed value: -{
-  "type": "string"
-}
```
removedOutput schema / properties / data_base64
```
Removed value: -{
-  "type": "string"
-}
```
addedOutput schema / properties / expiration_seconds
```
Added value: +{
+  "type": "integer"
+}
```
addedOutput schema / properties / url
```
Added value: +{
+  "type": "string"
+}
```

changedOutput schema / required

Previous value: -[
-  "content_type",
-  "data_base64"
-]New value: +[
+  "expiration_seconds",
+  "url"
+]

First observedSep 14, 2026

TDQS

A4.3/5.0

Behavior5/5

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

Annotations already declare read-only, idempotent and non-destructive, so the safety profile is covered; the description goes further by disclosing that the URL is short-lived (expires), that the response is url plus expiration_seconds rather than bytes, and that it works for both sent and received faxes. These are behavioral traits an agent cannot get from the annotations or schema and materially change how it should handle the result.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads what is returned, then gives the imperative handling steps, then the side-effect caveat. Every sentence is actionable and there is no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists so return values needn't be spelled out, yet the description still flags the return shape (url, expiration_seconds) and the short-lived nature that drives the save-immediately instruction. Combined with the 100%-covered schema and read-only annotations, an agent has everything needed to call and handle this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all three parameters (fax_id, format, user_id) are already documented in the schema, and the description adds no format syntax or defaulting nuance beyond it. Baseline 3 is appropriate when the schema carries the parameter burden.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Return a short-lived URL for a sent or received fax file (pdf or tiff)'. It also implicitly separates itself from metadata tools like get-fax by clarifying it returns a URL, not file bytes. However, no sibling tool (get-file-page, get-fax-thumbnail, get-fax) is named as the alternative, so differentiation requires inference.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete operating instructions: save the URL to disk immediately, don't paste file bytes into conversation, open the saved file when the user wants to view it. What's missing is when to choose this over get-file-page (paged content) or get-fax-thumbnail, which are the most plausible confusions among 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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