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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds genuinely new context: 'Deterministic' (identical input yields identical output) and 'Result carries a signed receipt', which tells the agent the output is externally verifiable (relevant to receipt_verify). It stops short of explaining what the flags mean or rate limits.

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?

One compact sentence plus two short clauses, front-loaded with the deterministic-facts claim and immediately followed by the critical disambiguation and receipt note. No filler; every clause carries information.

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?

An output schema exists, so return values need no elaboration, and annotations cover the safety profile. The description adequately frames what the tool does and what it is not. A minor gap remains around how to read the selectors/flags, but overall it is complete for its complexity.

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 100% and the single enum parameter is documented ('Only base is supported'), so the schema carries the semantics. The description adds no address format or chain detail beyond the schema, making the baseline 3 appropriate.

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+resource (Base contract facts) and enumerates exactly what is returned: ERC-20 metadata, proxy slots, owner(), privileged-function selectors and flags. It also disambiguates from the misleading name by stating 'Not a safety verdict', which separates it from siblings like sanctions_address_screen or erc20_balance.

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?

The phrase 'Not a safety verdict' implies a usage boundary (don't use this for safety screening) but does not name an alternative sibling or state the positive condition that selects this tool over checking a balance or price. Usage is implied rather than explicit.

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