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

With no annotations provided, the description carries the full burden. It discloses automatic cost deduction and mandates copying the exact cost/balance line from the result footer. This is significant behavioral context beyond basic execution, though it does not cover failure modes or side-effect specifics.

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 somewhat long but every sentence earns its place, especially the CRITICAL billing receipt instruction which is essential for correct assistant behavior. The main action is front-loaded and the workflow is logically ordered. Slight verbosity around the 'CRITICAL' block prevents a 5.

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 tool executes arbitrary tools, and the description covers the essential context: prerequisite discovery, cost deduction, and the mandated receipt handling. Given the absence of an output schema and the variable nature of results, this is a complete description for real-world use. It could mention error handling, but that is minor.

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 descriptions cover all three parameters with meaningful guidance: slug from xpay_discover, tool from xpay_details, and arguments as key-value pairs. The description adds an example for arguments but does not go beyond the schema. Baseline 3 is appropriate given the high 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 opens with 'Execute any tool on any XPay server', a specific verb+resource statement that clearly distinguishes this tool from siblings like xpay_balance, xpay_details, and xpay_discover. It unambiguously identifies this as the general-purpose execution tool.

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?

Provides explicit workflow guidance: 'Use xpay_discover to find servers and xpay_details to check required inputs before running.' This tells the agent when to use prerequisite tools and implies xpay_run is for after discovery and validation. No exclusions are needed for a generic executor.

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