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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description is not repeating them. It adds genuinely useful non-schema behavior: provenance of the data (the precompile), a concrete price ($0.02/call over x402), the x-credit-token header alternative for unlimited calls, and the explicit note that no API key is required and no free tier exists.

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?

Three sentences, front-loaded with the payload description followed by sourcing, input, and payment mechanics. There is mild redundancy between 'Full profile of a Base-native B20 token' and 'Complete B20 token profile' in the same sentence, but no padding beyond that.

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 an output schema present, the description needn't explain return values, and it covers the remaining essentials: what class of data, the authoritative source, the required input, and the payment/credit model. The one gap is the lack of any routing against closely overlapping B20 siblings, which matters given how many exist.

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?

Only one parameter and schema description coverage is 100%, so the schema already fully documents 'address'. The description's 'Required input: address' restates the schema's required array without adding format, chain, or validation meaning, which is the expected baseline-3 outcome when the schema does the heavy lifting.

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+resource (full profile of a Base-native B20 token) and enumerates exactly which fields are returned (variant, name, symbol, decimals, supply, cap, policies, pause states, rebase) plus the data source ('straight from the precompile'). It partially differentiates from b20-safety as the 'data companion', but does not distinguish itself from overlapping siblings like b20_metadata, b20_dossier, b20_supply, or b20_rebase.

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?

Signals an implied usage context by calling itself the 'data companion to b20-safety', suggesting a read-the-data role versus a risk-assessment role. However, there is no explicit when-to-use guidance and no routing statement telling the agent when to prefer b20_metadata, b20_dossier, or b20_supply instead.

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