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

With minimal annotations (all false hints), the description carries the main transparency burden. It adds meaningful behavioral context: the invoice expires after ttlSeconds (default 24h) and the tool returns an invoiceId and payUrl. This goes beyond the annotations but does not cover potential side effects or failure modes, so a 4 is appropriate.

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 and front-loaded: the first sentence states the core purpose, followed by the workflow, return values, and expiration. Every sentence adds distinct value with no redundancy or fluff.

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?

The description gives a complete workflow context for a tool with 7 parameters and an output schema: it explains the agent-to-agent payment flow, the return values, and the expiration behavior. The schema fills in parameter details and the output schema defines return structure, so the description does not need to repeat that. Minor edge cases (e.g., currency behavior or callbackUrl) are not detailed, but that's acceptable given the schema's coverage.

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?

All 7 parameters have schema-level descriptions (100% coverage), so the schema already provides parameter semantics. The description only mentions the ttlSeconds default, which is also in the schema, and adds no new meaning for the parameters. Baseline 3 applies.

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 states a specific action ('Create an agent-to-agent invoice') and the resource it acts on, with a clear statement of the caller's role ('Agent A calls this to request payment from Agent B'). It explicitly positions the tool against sibling tools by referencing invoice.pay as the settlement step, making its 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 clearly specifies when to use the tool ('Agent A calls this to request payment from Agent B') and the complementary use of invoice.pay for the payer. However, it does not explicitly mention when to avoid using this tool (e.g., when an invoice already exists, use invoice.get), so it stops short of a perfect score.

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