Calculate SAP x402 Cost

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

Annotation contradiction: readOnlyHint=false conflicts with description stating 'Pure local cost calculation; does not read chain state,' implying a read-only pure function. This inconsistency undermines trust in behavioral accuracy.

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?

Three compact sentences: core purpose, flow context, and usage advice. No wasted words, front-loaded with the most critical information.

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?

Given the annotation contradiction, the agent cannot reliably determine side effects. Output schema exists (not shown) so return values are covered. The description provides flow context but the contradiction is a critical 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 provides 100% description coverage for all 4 parameters. Description adds no additional parameter detail beyond the schema, so baseline score 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?

Description clearly states the tool performs a local cost calculation using SDK X402Registry.calculateCost and does not read chain state. This verb-resource pair is specific and distinguishes from siblings like sap_x402_estimate_cost.

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?

Description provides clear context: it flows in 'Payment and settlement flow' and should be used 'before creating escrows or settling calls.' It also hints at prerequisites (signer mode, policy) for subsequent write ops, but does not explicitly exclude alternatives or state when not to use.

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