render_diagram

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

Annotations provide readOnlyHint=true, but the description adds valuable behavioral context beyond that: it relies on the external mermaid.ink service, returns a /tmp path, and explicitly states no approval is needed. This is consistent with the annotations and adds operational clarity.

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 short sentences, each carrying essential information: the action and target, the output location, and the approval requirement. There is no wasted wording or redundancy.

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 simple one-parameter tool with a read-only annotation, the description covers what the tool does, how it operates (via mermaid.ink), where the output goes (/tmp path), and whether approval is needed. No critical information is missing for invoking it correctly.

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?

While the schema only defines a single 'spec' string with no description, the tool description compensates by identifying it as a 'Mermaid diagram spec'. This gives the parameter meaning beyond the bare schema and is sufficient for a single-parameter tool, though no examples or constraints are provided.

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 ('Render') and resource ('Mermaid diagram spec as PNG via mermaid.ink'), clearly distinguishing it from sibling tools like render_chart. It also states the output location ('/tmp path'), making the tool's purpose unambiguous.

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 clearly implies when to use the tool (when a Mermaid diagram spec needs to be rendered as PNG) and adds an operational note ('No approval needed'). It does not explicitly name alternatives or exclusions, but the context is clear enough for an agent to select this tool over siblings.

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