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

Annotations already declare read-only, idempotent, non-destructive behavior, so the bar is lower. The description still adds real value: the output is an image plus the underlying text and sources, a source line is stamped on the image, and it degrades gracefully by returning text if drawing fails.

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 action and output type, with the failure-mode caveat last. Every clause earns its place and nothing is padded.

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?

With a full output schema and 100% parameter coverage, the description need not restate return values or param formats, and it still covers output composition and failure behavior. Only the when-to-use routing is thin, which is a minor gap.

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 description coverage is 100%, including detailed enum semantics and place-code formats, so the schema carries the parameter burden. The description adds no format or syntax detail beyond what the schema already documents; baseline 3 is appropriate.

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 ('Draw a chart (PNG)') and enumerates the exact four chart kinds that match the kind enum, so an agent immediately understands the scope. No sibling tool draws images, so this is clearly differentiated from income, demographics, etc.

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 phrase 'of a tool result' implies this wraps/enriches the data tools (income, opportunity), but the description never explicitly says when to prefer a chart over the bare numeric tool, nor names alternatives or exclusions. Usage is inferable but not stated.

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