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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the description isn't needed for the safety profile. It adds real value beyond that: it discloses the key behavioral guarantee that unmatched addresses are reported as unlabelled and never guessed, plus the pricing model ($0.005/call over x402, prepaid header for unlimited, 1 free call/day, no API key).

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-loads the purpose with a punchy framing sentence, then layers mechanism, guarantee, input, and pricing in a sensible order. Slightly long and the rhetorical question framing costs a little space, but every subsequent sentence 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 needn't be spelled out, and the description still explains what it reads and how unmatched cases are handled. For a one-param tool with full schema and annotation coverage, this is nearly complete; only sibling differentiation is missing.

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 coverage is 100% for the single parameter, so the schema already documents 'address'. The description merely restates 'Required input: address' without adding format, checksum, or chain constraints. Baseline 3 applies 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?

The description states a specific verb+resource — 'label / identify what this Base address is' — and details the mechanism: matching a sourced registry and reading chain state (contract vs EOA, ERC-4626, Safe, DEX pool). It is clearly distinct from a generic lookup, but it never explicitly names or contrasts with near neighbors like address_intel or address_check, which is what would earn 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?

Usage is implied rather than stated: the agent can infer 'use this when you have an unknown Base address and want to know what it is.' There is no explicit when-to-use, when-not-to-use, or alternative-tool routing despite numerous sibling address tools that overlap in surface area.

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