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

With no annotations provided, the description carries the full behavioral disclosure burden and does so thoroughly. It reveals the URL length limit of 16000 characters, the url_ok flag, the DEFLATE-based algorithm, the custom 64-character alphabet, and the POST-vs-GET API distinction with size limits. This is rich, non-obvious behavioral context that an agent needs to avoid misuse.

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 and front-loaded: the first sentence states the core purpose, followed by critical usage constraints, the alternative tool, and a caveat against base64 confusion. Every sentence carries necessary operational information, with no filler or redundant 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?

The description is complete for the tool's complexity: it covers the operation, output type, size limits, fallback behavior, and encoding specifics, all without an output schema. An agent can determine whether and how to invoke encode_source correctly, and knows exactly when to route to render_diagram instead.

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?

The input schema has 0% description coverage and only declares 'text' as a string, so the description must compensate by explaining what text means. The description clarifies that text is PlantUML source, which is essential semantic context not present in the schema. It does not fully elaborate edge-case format requirements, but for a single-parameter tool this is adequate.

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 a specific verb and resource: encoding PlantUML source into a URL token and ready-to-use SVG/PNG share/render URLs. It also distinguishes itself from related siblings like render_diagram and decode_token by explaining what it is not and which sibling handles the alternative operation.

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 gives explicit when-to-use and when-not-to-use guidance: when url_ok is false, do not share the URLs and instead use render_diagram, which uses the POST API with no size limit up to 5 MB. It also explicitly warns against using base64 codecs and directs users to encode_source/decode_token instead, naming alternatives and conditions clearly.

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