Registers a local file as a reference image for other image tools and returns a file_uri to pass as additional_image_paths.
Register a local file for use as a reference image in other tools (e.g. tool_transform_image). Returns a file_uri to pass as additional_image_paths.
| Name | Required | Description | Default |
|---|---|---|---|
| params | Yes |
Changes observed during successful MCP inspections.
v3.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It does disclose the return artifact (a file_uri for additional_image_paths), which is valuable given there is no output schema. However it is silent on the semantics of 'register' — whether the file is copied or merely referenced, whether the source path must remain valid, size/format limits, or any permission requirements.
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?
Two tight sentences with the purpose front-loaded and the return value second. No filler or restatement of the tool name.
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 single-argument setup tool with no annotations and no output schema, the description covers the two things an agent most needs: why to call it and what it returns. Missing only edge-case behavior (file lifetime, format restrictions, whether the path is copied), which is minor at this complexity level.
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 on the top-level parameter ('params') is 0%, and the description adds no parameter-level detail: it never mentions file_path, mime_type, or display_name. 'Local file' only loosely implies file_path. The nested $defs do document the inner fields, which prevents this from being a 1, but the description does not compensate for the coverage gap.
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?
Specific verb+resource ('Register a local file') plus the exact role it plays: producing a reference image for other tools. It names a concrete sibling (tool_transform_image) as the consumer, so an agent can distinguish this precondition/setup tool from the media-generation siblings without opening a 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?
States the usage context clearly ('for use as a reference image in other tools') and gives a concrete example consumer plus the parameter name downstream tools expect. It does not state when NOT to use it (e.g. when the file is already registered or when a remote URL suffices), so it falls short of full when/when-not guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.