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

No annotations, so the description carries the full behavioral burden. It does convey that this is a read (non-destructive) and adds real context the schema cannot: the supported chains and the "5 free trial calls per signed wallet" cost/auth model. However, it omits return shape, failure behavior for non-ERC-20 inputs, and chain defaults.

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 single sentence with the verb and resource first, plus a short pricing note. No filler; the emoji is cosmetic but does not obscure meaning.

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 annotations, no output schema, and 0% parameter coverage, the description should carry much more. Chain options are the only added detail; defaults, token identifier format, response contents, and error cases are all absent for a tool whose structured fields are entirely bare.

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 none of the 3 params are documented. The description partly compensates by enumerating the valid chain values (Base or Ethereum), but it never clarifies the critical token-vs-address distinction or which parameter is required when, leaving two of three params ambiguous.

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 ("Reads") and resource ("an ERC-20 token's decimals value") with scope ("on Base or Ethereum"), which cleanly distinguishes it from siblings like x402-token-total-supply or x402-token-symbol. It doesn't explicitly name those siblings, so it stops short of a 5.

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?

No when-to-use guidance, no exclusions, and no alternatives named. An agent scanning the huge x402-token-* sibling list gets no signal about why to pick token-decimals over erc20-info or token-intel.

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