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

With no annotations, the description carries full behavioral disclosure. It explains return types for both formats, the default, the shareable URL, and the error contract with line, column, hint, and help link. It does not cover network failures, rate limits, or side effects of creating a shareable URL, but it is substantially transparent.

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?

Three sentences, no filler, and the core action is front-loaded. Each sentence adds a distinct piece of information: output types, the format/default behavior, and error handling.

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 two-parameter tool with no output schema, the description covers the main return behavior, error shape, and format options well enough for an agent to call and interpret results. It could be slightly stronger by explicitly routing validation-only needs to validate_diagram, but it is close to complete.

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 only 50%, but the description compensates by explaining what format values produce ('PNG image block' vs 'SVG markup as text') and confirming the default. The text parameter's PlantUML requirements are already in the schema, so the description adds the important missing semantics for format.

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?

States a specific verb and resource ('Render PlantUML source text to a diagram image') and distinguishes itself from sibling tools like validate_diagram and list_diagram_types by focusing on actual rendering. The description also clearly delimits the output formats.

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 makes the tool's purpose and behavior clear, but it never explicitly addresses when to choose this tool over validate_diagram or get_syntax_reference. The integrated validation behavior implies a use case, but no exclusions or alternative routing are stated.

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