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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so safety is covered. The description adds value beyond them: it states the call is free, characterizes the list as 'limited', notes that entries carry sources and check dates (staleness context), and warns that a match is not proof of authenticity.

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 with the key qualifier ('Free.') front-loaded and the content enumeration following. The field list is somewhat dense but each item is informative rather than redundant; nothing reads as padding.

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 zero-parameter read-only reference lookup with an output schema, the description supplies the necessary scope (what tables exist) and the crucial limitation (a match is not proof of authenticity). An agent has enough to decide when the lookup is worthwhile and how much to trust it.

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?

The tool takes zero parameters, which is the baseline-4 case; there is nothing for the description to disambiguate. The enumerated return fields (network, contract, symbol, decimals) are descriptive of output rather than input, so they add no parameter meaning.

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?

The description names a specific resource and enumerates its contents: known assets (network, contract, symbol, decimals) with sources and check dates, CAIP-2 networks, x402 scheme names, and payment flows. It is clearly distinguishable from get_receipt or x402_parse_payment_request, though it never names those siblings to route the agent 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 only implied: the 'Free.' prefix signals cost-free lookup and the closing caveat warns that a table match is not proof of genuineness. There is no explicit statement of when to call this versus the sibling tools, nor any prerequisites or exclusions.

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