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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context about billing and quotas: 'Paid via x402 or API key credits. Free tier: 20 simulate calls/day per client.' This goes beyond the annotations and helps the agent understand cost implications. No contradiction with annotations.

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: two sentences, zero wasted words. It front-loads the core purpose in the first sentence and adds the critical billing/rate-limit context in the second. Every sentence earns its place.

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 tool with 4 parameters, nested objects, and no output schema, the description is complete enough: it identifies the three output components (cost, failure risk, side effects) and covers key usage context (pricing/free tier). While it doesn't describe return formatting or error cases, the core information needed to invoke and interpret the tool is present.

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 the input schema fully documents all parameters. The description does not add any additional parameter-level meaning beyond what the schema already provides, meeting the baseline for good schema coverage.

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's function: 'Estimate cost, failure risk, and notable side effects for a proposed action.' This specific verb+resource combination distinguishes it from siblings like risk_score, which likely only provides a risk score, and balance/top_up, which deal with funds. The scope is explicit and 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 implies usage for pre-action evaluation ('for a proposed action') and mentions payment/rate limits, but it does not explicitly state when to use this tool versus alternatives like policy_gate or risk_score. No exclusions or alternative tools are named, so guidance is only implied rather than explicit.

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