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

With no annotations, the description still discloses a lot: the data source and its fallback chain (GeckoTerminal, then DefiLlama), the payment mechanism and price, and the per-caller free quota. What it omits is behavior on failure or missing tokens (unknown token, no liquidity, stale data), which matters for an agent relying on a price.

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?

Two sentences, front-loaded with the resource and returned fields, then a compact second sentence covering source fallback, cost, and quota. No filler and nothing restated from the schema.

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 no-output-schema read tool it covers what comes back (including the 'where available' caveat on liquidity/FDV), where the data comes from, and what it costs to call. The remaining gap is error/no-data behavior, which is minor but not zero for a paid lookup.

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 0% for the single required 'address' parameter, so the description must carry the load. 'By contract address' does useful work — it tells the agent this is a token contract on Base, not a wallet or symbol — but nothing is said about format, checksumming, or whether the chain must be specified.

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?

Specific verb+resource: 'Current USD price of a Base token by contract address', with the returned fields enumerated (24h change, volume, liquidity/FDV). It is clearly distinguishable from sibling base_token_risk by what it returns, though it never names that sibling explicitly.

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 (call it when you need a live token price) and the cost model — $0.005 USDC via x402 with 3 free calls/day — gives practical guidance about when calling is cheap versus expensive. There is no explicit when-to-use / when-not-to-use statement or routing to base_token_risk or fx_rates.

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