thumbnail

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

No annotations are provided, so the description bears full responsibility for disclosing behavior. It states that the tool extracts a thumbnail, which is a read operation, but it does not mention failure modes (e.g., what happens if no thumbnail exists), whether it returns the first/largest thumbnail, or any rate limits or permission requirements. This leaves significant behavioral uncertainty.

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 a single, clear sentence with no filler words. It is concise and front-loads the core action (extract thumbnail) and output format, though it could benefit from a brief note about the input parameter to be more structured.

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 tool has two parameters (one nested), no output schema, and no annotations, the description is too sparse to be complete. It does not explain the return value structure, error handling (e.g., missing thumbnail), or how to choose among the image kind options. The sibling tools all operate on image metadata, and this description does not help the agent understand how this extraction fits into a workflow.

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 0%, so the description must compensate for parameter meaning. It hints at the 'url' boolean by mentioning 'base64 data or URL', but it does not explain the 'image' object structure, its 'kind' enum, or how to specify the source image. The schema field names are self-explanatory but the description adds minimal clarification beyond them.

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 a specific verb ('Extract') with a clear resource ('embedded thumbnail') and output format ('as base64 data or URL'). This clearly distinguishes it from sibling metadata readers like read-metadata or read-exif, which focus on metadata fields rather than extracting image data.

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 implies usage when an embedded thumbnail is needed, but does not explicitly state when to use this tool versus the sibling metadata tools, nor does it mention any exclusions or alternatives. It provides no direct comparison or guidance for selecting between similar tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.