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

Annotations already cover safety (readOnlyHint=true, destructiveHint=false, openWorldHint=true). The description adds genuinely useful non-schema behavior: the data source (DefiLlama), that results include confidence and a timestamp, and that the call costs $0.003 USDC on Base via x402 — a non-obvious billing constraint an agent must know.

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-loaded with the resource and scope, then the source, output fields, and price. It is dense but every clause carries information; only the examples repeat the schema. 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 one-parameter read tool with no output schema, the description covers source, currency, input identifier, returned fields (price, confidence, timestamp), and cost. Complete enough to invoke correctly; a note on rate limits or multi-coin call limits would fully close the gap.

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 coverage is 100% and the single 'coins' parameter is fully documented in the schema, including its comma-separated format and example. The description restates the CoinGecko-id convention but adds no syntax or validation detail beyond what the schema already provides, so the baseline 3 applies.

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 specific verb+resource ('Current USD spot price for one or more crypto assets'), the identifier system (CoinGecko id), and the upstream source (DefiLlama). This is clearly distinguishable from siblings like crypto_balance, crypto_gas, or crypto_token_report, which cover different crypto data.

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?

Usage is implied by the resource ('spot price') but there is no explicit when-to-use, when-not-to-use, or named alternative such as crypto_token_report for richer asset data. The paid-call cost hints that it should be called deliberately, but no routing guidance is given.

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