Use any image file to use as thumbnail. Once you use the API, you will get upload_url in the response, and that can be used to upload the image file.
Here is the sample curl request.
curl --location --request PUT '<upload_url>' \
--data '<YOUR_FILE_PATH>'| Name | Required | Description | Default |
|---|---|---|---|
| asset_ID | Yes | An asset id for the previously created asset. |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds meaningful behavioral context beyond annotations: calling the API returns an upload_url, and the actual image file must then be PUT to that URL. This two-step flow is not covered by the annotations, which only indicate non-read-only, non-destructive behavior.
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 first sentence is awkwardly phrased and the embedded curl example, while helpful, makes the description longer than necessary. The core purpose is front-loaded but not as tightly as it could be.
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?
For a simple one-parameter tool with an output schema, the description covers the upload flow adequately. However, it omits sibling differentiation and usage context, leaving an agent without clear guidance on when this tool is preferred over thumbnail_upload_live or thumbnail_select.
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 the schema already fully documents the single asset_ID parameter. The description adds no additional meaning or constraints for that parameter.
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 'Use any image file to use as thumbnail' implies thumbnail uploading but does not explicitly state the verb+resource as 'upload a thumbnail for a specific asset.' It also fails to differentiate from siblings like thumbnail_select or thumbnail_upload_live.
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?
No guidance on when to use this tool versus alternatives such as thumbnail_select or thumbnail_upload_live. The curl example describes a technical step but not the context in which this tool should be selected.
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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