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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds behavioral context beyond annotations by specifying that it returns a hosted URL and supports a self-hosted Kroki backend, which helps the agent understand the output format and service dependency.

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 concise (two sentences plus an example) and front-loaded with the primary verb and purpose. Every sentence adds value, and the example is practical. There is no fluff or repetition.

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's simplicity (3 params, 1 required, output schema present), the description is complete for an agent to select and invoke it correctly. It explains the return format, supported diagram languages, and embedding use case—covering all necessary context.

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 coverage is 100%, with each parameter having a description. The tool description adds minimal additional meaning—only an example of the 'source' parameter and a note on format types, which are already present in the schema. The schema carries the heavy lifting.

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 clearly states the tool's function with a specific verb ('Turn diagram-as-code into an image'), lists supported formats (Mermaid, PlantUML, Graphviz/DOT, C4, Excalidraw, etc.), and explains the return value (a hosted SVG/PNG URL). This distinguishes it from sibling tools, which focus on text, data, or model operations.

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 provides clear context: it is for converting diagram-as-code into an image for embedding in Markdown/HTML. It offers an example GET request but does not explicitly exclude alternatives or compare to other tools. Since sibling tools are thematically distinct, the intended usage is obvious.

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