bill_graph

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

Annotations already declare readOnlyHint=true and idempotentHint=true, establishing a safe read operation. The description adds value by clarifying the output is an image, which is meaningful behavioral context beyond the annotations, though it does not detail image format or size, which is acceptable for this simplicity.

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 exceptionally concise, consisting of two sentences that front-load the core purpose and immediately provide an alternative usage. Every word is purposeful, with no redundancy or filler.

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 rendering tool, the description is complete: the schema fully documents parameters, annotations cover safety, and the description clarifies output type and provides a pointer to the data sibling. No output schema is needed since the return is an image, and the context is fully covered.

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% for both parameters, with bill_id and graph_type each having basic descriptions. The tool description itself does not add further parameter details, so the baseline of 3 is appropriate; schema carries the semantic weight.

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 renders a bill graph as an image, using a specific verb and resource. It also distinguishes from sibling tool bill_graph_data by noting that the data tool should be used for underlying numbers, making the 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 explicitly provides usage guidance by stating 'For the underlying numbers rather than a picture, use bill_graph_data.' This directly tells the agent when to choose this tool versus an alternative, fulfilling the criterion for explicit when/when-not guidance.

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