bill_graphRender a network bill's usage as a graph image by providing bill ID and graph type: bits, monthly, hour, or day.
Render a bill graph as an image.
For the underlying numbers rather than a picture, use bill_graph_data.
| Name | Required | Description | Default |
|---|---|---|---|
| bill_id | Yes | Bill ID | |
| graph_type | Yes | Graph type: bits, monthly, hour, or day |
Changes observed during successful MCP inspections.
v1.11.1Output schema / (root)Previous value: -{
- "additionalProperties": true,
- "type": "object"
-}New value: +nullv1.9.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds that the output is an image, but it does not disclose details like image format, response wrapping, or any other behavioral traits. This is adequate but not rich.
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 short sentences, front-loaded with the core action, and no filler. The alternative is mentioned in a single clarifying sentence, making the definition both concise and well structured.
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 two-parameter tool with full schema coverage and safety annotations, the description tells an agent everything essential: what it produces (image), and what the alternative is for data (bill_graph_data). No critical details are missing for correct invocation.
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%, so both bill_id and graph_type are already documented in the schema. The description does not add parameter-level meaning beyond what the schema provides, so the baseline of 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?
The description clearly states a specific action and resource: 'Render a bill graph as an image.' It also distinguishes itself from the sibling bill_graph_data, which provides numbers, so an agent can immediately understand what this tool produces.
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 tells the agent when not to use this tool: 'For the underlying numbers rather than a picture, use bill_graph_data.' This clearly names the alternative and the condition for choosing it, leaving no ambiguity about tool selection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.