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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false. The description adds meaningful behavioral context: cost ($0.001 USDC per successful call via x402 on Solana) and an equivalent HTTPS endpoint, with no contradiction.

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?

Front-loads the core predicate, then gives the Grundy clarification, a worked example, the n range, and payment/endpoint details. The sentences are short and earn their place, though the endpoint/payment detail is somewhat ancillary.

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 simple two-parameter read-only computation with no output schema, the description supplies the range, a worked example, implied boolean return semantics, and access/payment details. It leaves some moves-array constraints to the schema but is broadly complete for this tool's complexity.

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 0%, so the description must carry parameter meaning. It explains n's range (0-500) and demonstrates moves as a set of allowed subtraction values, but does not document the moves array constraints (1-8 items, each 1-100) or clarify ordering/duplicates. Partial compensation only.

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?

States a precise predicate: whether the player to move wins a subtraction game on heap n with perfect play, and clarifies that a win means nonzero Grundy value. It distinguishes win/loss from the raw Grundy value via examples, though it does not explicitly name the sibling subtraction_grundy.

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 useful context such as n's 0-500 range, example moves {1,2,3}, and pricing, but does not say when to choose this over subtraction_grundy or subtraction_row, nor state any exclusions. Usage is implied rather than explicitly guided.

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