media_postUpload an image, video, or audio file to Mastodon. Include alt text for accessibility.
Upload a media file (image, video, audio) to Mastodon.
| Name | Required | Description | Default |
|---|---|---|---|
| file_path | Yes | Absolute path to the media file to upload. | |
| description | No | Alt text / accessibility description for the media. |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v1.0.5Input schema / additionalPropertiesAdded value: +falseInput schema / properties / description / anyOfAdded value: +[
+ {
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+]Input schema / properties / description / defaultAdded value: +nullInput schema / properties / description / typeRemoved value: -"string"Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "result": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "result"
+ ],
+ "type": "object",
+ "x-fastmcp-wrap-result": true
+}v1.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this is a non-read-only, non-idempotent, non-destructive open-world write, so the safety profile is covered. The description adds only the accepted file types and nothing else — no note that it returns a media identifier for later attachment, no size/rate limits, no handling of duplicate uploads.
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?
A single front-loaded sentence with no filler or redundancy. It is efficient, though the brevity that helps here is exactly what leaves usage and behavioral gaps elsewhere.
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?
An output schema exists, so return-value explanation is not required. However, for an upload tool in a large Mastodon toolset, the description omits how the result connects to status_post and gives no constraints on file size or format, making it only minimally complete.
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 parameters are already documented with clear descriptions for file_path and alt text. The description's mention of image/video/audio adds a small amount of type context but nothing beyond the schema baseline, so 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 states a specific verb (upload), resource (media file), accepted types (image, video, audio), and destination (Mastodon). It is unambiguous versus list/read siblings, though it does not relate itself to status_post, which is the natural consumer of an uploaded media ID.
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?
There is no when-to-use guidance, no exclusions, and no mention of an alternative. An agent is not told that this is typically a prerequisite step before attaching media to a status, leaving the workflow to inference from sibling names alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.