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

Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds substantial context beyond that: the call is paid at $0.003 via x402 with the accepted chains, and critically that 'Over MCP this tool answers with that price and URL, not the data' — a non-obvious behavior that would otherwise cause an agent to misread the response. It also discloses the fuzzy 'best search match' semantics of a symbol query.

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?

The core capability and cost/caveat are front-loaded and every sentence carries information. The x402 payment sentence with the full endpoint URL and chain list is dense but justified, since it determines whether an agent can actually retrieve the data.

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 lookup with no output schema, the description covers the value proposition, the disambiguation prerequisite, the sibling to use instead, the price and payment rails, and the MCP-vs-HTTP return difference. Nothing an agent needs to call it or interpret the response correctly is missing.

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 parameter is documented, so the schema does the baseline work. The description still adds real meaning: a symbol resolves to the 'best search match' (implying possible ambiguity) while a mint address disambiguates, which is not stated in the schema's terse 'Symbol (e.g. CAPY) or mint address.'

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?

Opens with a specific verb and resource plus scope: 'Look up ONE X1 token by symbol or mint address,' then enumerates the returned fields (price in XNT and USD, holders, liquidity, 24h volume, 24h change). It explicitly separates itself from top_tokens for ranked lists, so an agent can route between the two without opening either schema.

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?

Gives concrete when-to-use conditions: a symbol is fine by default, but 'when several tokens share a ticker, run impostor_check first and pass the mint' names the prerequisite and the alternative tool. It also states the exclusion ('For a ranked list use top_tokens'), so both the positive and negative routing cases are covered.

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