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

With no annotations, the description carries the full burden and does a solid job: it discloses the exact cost, both accepted payment chains, that no credentials or account are required, and that failed calls are not billed. It stops short of describing response shape beyond field names, latency, or rate limits.

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?

Four short front-loaded clauses: what it returns, what it costs, how billing on failure works, and the endpoint URL. Every sentence earns its place; only the opening 'Paid.' fragment is slightly clipped.

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-parameter, no-output-schema price lookup, the description covers the essential decision inputs: what data comes back, the price, the payment rails, and the failure-billing rule. Only the exact response envelope and error modes are left unstated, which is minor at this 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?

The tool takes zero parameters, so the schema is fully self-explanatory and the description correctly introduces no parameter semantics. Nothing is missing on this dimension.

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?

Names a specific resource (Swop / SWOP) and enumerates exactly what the call returns: live USD price, 24h change, and market-cap rank. The verb is implicit ('price'), and it doesn't distinguish itself from the large buy_coin_* / buy_crypto_price families, but the token-specific scope is 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 commercial framing ('Paid', '$0.01 USDC on Base or Solana', 'No account, no API key') implicitly tells an agent this is a low-cost single-token lookup, and 'Failed calls not charged' lowers risk. However, there is no explicit when-to-use or when-not-to-use guidance relative to siblings such as buy_coin_SWOP-style lookups or buy_crypto_price.

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