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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered structurally. The description adds non-obvious context: no account is required and reading itself costs nothing, which matters for a tool about paid endpoints, plus it summarizes the return shape.

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 its meaning, then usage, then usage-vs-alternative, then safety, then return values. Dense but every sentence carries information; it runs slightly long for a one-parameter tool but nothing is 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?

With no output schema, the description usefully enumerates returned fields (resource URL, price, asset, network, price history), and annotations cover the safety profile. The gap is that the advertised filters are unbacked by the schema, leaving a mismatch an agent must resolve at call time.

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 description coverage is 0% and the single parameter (limit) is never explained in the description. Worse, the description advertises 'filters for price ceiling and origin' that do not appear anywhere in the input schema, which can mislead an agent into expecting parameters that cannot be passed.

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 verb and resource (x402-priced endpoints) and immediately enumerates what the listing carries: price per call, network, asset, price history. It explicitly distinguishes itself from search_agents by the axis of comparison (cost vs. capability).

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 two concrete use cases (compare cost across providers, find the cheapest) and names the alternative tool with the condition that selects it ('search_agents is better for finding a capability by what it does'). Clear when-to-use and when-not-to-use.

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