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

Annotations already declare readOnly/idempotent/non-destructive, and the description usefully adds the critical behavioral fact that this tool returns a payment request but does NOT execute payment. It also discloses the cost and accepted networks, going beyond structured fields.

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?

Purpose is front-loaded and the key caveat ('This tool does not pay') is isolated for emphasis. Slightly verbose in enumerating return fields that an output schema already covers.

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?

An output schema exists, yet the description nonetheless summarizes the payload and the payment requirement, so an agent knows both what it gets back and what it must do next. Complete for a two-param prepare tool.

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% and both parameters are documented there, so the schema carries the load. The description restates the 'past window official outcome' meaning of start but adds no format or syntax detail beyond the schema.

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?

Starts with a specific verb+resource ('Returns the x402 payment request for Polymarket crypto Up/Down data') and enumerates the assets, timeframes and chains. It is clearly distinguishable from the surrounding bridge_*/stocks_*/x402_check siblings.

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?

Gives clear operational context: 'Pass start (unix) for a past window's official outcome' and 'Pay it with your own x402 client. This tool does not pay.' It does not name an alternative sibling tool or state explicit exclusions, but the when-to-use condition is unambiguous.

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