Pay for and call a service

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

The description claims 'Idempotent on retry,' but annotations state idempotentHint=false. This direct contradiction severely undermines transparency. Additionally, despite adding some behavioral context (payment receipt, limit enforcement), the contradiction is a critical failure.

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 concise with 4 sentences, front-loading the primary purpose. It could be slightly trimmed, but it efficiently covers key points.

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 presence of an output schema for return values, the description adequately covers the tool's behavior (idempotency, limits, confirmation, receipt). It is sufficiently complete for an agent to understand the tool's role.

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 high (80%) so baseline is 3. The description adds minimal value beyond schema: it mentions maxPrice enforcement and idempotency, but these are already implied by the schema descriptions.

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 purpose: paying for and calling an Obol metered service via Circle Gateway. It distinguishes from sibling tools (deposit, find_service, etc.) by combining payment and service invocation.

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 provides context on when to use: mentions enforcement of per-call maxPrice and account spending limits, and near-limit confirmation. However, it lacks explicit guidance on when not to use or alternatives to this tool.

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