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

With no annotations, the description carries the full burden and does well: it explicitly declares the tool is side-effect free ('does not spend money or place a call') and discloses the downstream cost (0.50 USDC on Base, facilitator named in its 402). It omits any auth or rate-limit context, so not a 5.

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?

Two sentences, front-loaded with the '[FREE]' tag and the tool's purpose, then a second sentence covering returned artifacts and the no-side-effect guarantee. No filler.

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?

For a zero-param info tool with an output schema, the description supplies everything an agent needs: purpose, the artifacts returned, and the critical assurance that calling it spends nothing. Return-value detail is properly delegated to the output schema.

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?

Zero parameters, so the baseline is 4; there is nothing for the description to disambiguate and schema coverage is 100%. No param-level detail is needed or missing.

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 names a specific resource (Coin Duel entry info) and enumerates exactly what the tool returns: the register call, the x402 entry endpoint with its price/chain, the call endpoint, and the open rounds URL. It also distinguishes itself from action siblings by stating it does not spend money or place a call.

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?

States the context clearly ('exact steps for an agent to enter Coin Duel today') and implicitly routes the agent here before invoking the paid entry flow. It does not name a specific alternative tool (e.g., coinduel_rules) or state explicit when-not conditions, so it stops short of a 5.

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