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

Adds real context beyond annotations: 404 for missing contract, 422 for non-ERC-20, both uncharged, $0.01/call with first 25 free, and failed calls free -- which also explains the idempotentHint=false billing behavior. Runs long on pricing, but the error/billing disclosure is substantive for an openWorld read tool.

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 what the tool returns and its sibling distinction, with pricing/error details trailing. Dense but efficient; the pricing sentence is slightly over-weighted for a two-parameter read.

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?

No output schema exists, and the description enumerates return fields (raw amount, decimals, symbol, human-readable amount, live from contract). Error codes, billing, and safety are all covered, leaving nothing an agent needs to call correctly.

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%, so the baseline is 3. The description adds the 40-hex-character address format, but its claim that 'both inputs are 0x addresses' conflicts with the schema, which allows a ticker like USDC for the token parameter -- a minor inaccuracy rather than added clarity.

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 and resource ('ERC-20 token balance of a wallet on Unichain ... via balanceOf') and names the exact return fields. It explicitly distinguishes itself from the sibling 'unichain_balance' (native coin), so an agent can route without opening schemas.

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?

Gives a concrete usage context ('check stablecoin or token holdings before a transfer or trade') and names the alternative for the native-coin case ('for the native coin use unichain_balance'). The when-to-use and when-not-to-use are both explicit.

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