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

Annotations declare the tool read-only and idempotent. The description adds that it returns a stateless PNG URL and that a full Chart.js config can override labels/values, providing behavioral context beyond the annotation flags. No contradictions.

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?

Two sentences, front-loaded with the core transformation, then supporting details on chart types and URL form. No redundant phrasing.

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 covers purpose, chart types, and URL form, relying on schema and output schema for parameter and return details. However, it omits the 'doughnut' chart type listed in the schema, and doesn't address potential overlap with render_diagram, leaving minor gaps.

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 descriptions cover 100% of parameters, giving baseline clarity. The description adds a concise summary of the main inputs ('Labels + values') and notes the override semantics, plus the URL encoding format, offering marginal additional value.

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 converts labels and values (or a Chart.js config) into a chart PNG URL, listing supported chart types. It uses a specific transformation and resource, distinguishing it from siblings like make_badge or text_to_image.

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 context (stateless URL for embedding) but doesn't explicitly state when to use this tool over alternatives like render_diagram. No exclusions or alternative tools are mentioned, leaving usage guidance implied.

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