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

Annotations cover the safety profile (readOnly/openWorld), and the description adds material behavior beyond them: no API key, x402 pay-per-call in USDC/USDT on Base, and 3 free calls per wallet. It also discloses the aggregate return shape, though it does not mention rate limits or failure modes.

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?

Three compact sentences, capability first, then pricing/free-tier. Every sentence carries distinct information and nothing is padded, though the venue parenthetical is somewhat list-heavy.

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?

With no output schema, the description usefully enumerates the return fields (median, min/max, deviation, confidence) and explains the payment/access model for a paid tool. Coverage is strong; minor gaps remain around refresh/caching and error behavior.

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%, so all seven parameters (asset, quote, venues, wallet, api_key, x_payment, max_age_seconds) are already documented in the schema. The description reinforces the venue list and free-tier wallet mechanic but adds little syntax beyond the schema, so 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: 'Multi-venue median spot price for any major crypto asset' and names the four venues plus the aggregate outputs (min/max, deviation, confidence score). It is clearly distinct from a plain price lookup, though it does not explicitly contrast itself with the sibling market_spread.

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?

'One call instead of four' implies aggregation use, and the payment/free-tier note hints at how to make it work, but there is no explicit when-to-use vs. the sibling market_spread or any exclusions. Usage is implied rather than guided.

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