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

Beyond readOnlyHint/openWorldHint, the description discloses three non-obvious behaviors: results depend on which chains the operator's free Blockscout key unlocks, airdropped tokens may be spam, and billing is $0.002 per successful call via x402 with failures not charged. That is substantive operational context an agent cannot get from annotations, though it omits rate limits and response-size/pagination behavior.

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 tight sentences: what you get, which chains and under what condition, then pricing caveats. Return shape and cost — the two things an agent needs up front — are front-loaded with no filler.

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 explained, yet the description usefully summarizes them (largest-first, per-chain and overall USD totals). Combined with pricing and the spam caveat, an agent has enough to call correctly; only latency/quota expectations under a paid-by-call model are left implicit.

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 limit, chains and address are already documented with types and defaults. The description adds only the 'largest first' ordering hint and the chain-availability constraint on the chains parameter; it does not restate or enrich the parameters further, so baseline 3 applies.

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?

First sentence states a specific resource and scope: native + ERC-20 balances for one EVM wallet across Blockscout-indexed chains, with USD valuation and totals. It is clearly distinguishable from siblings like crypto_debank_wallet_portfolio or crypto_solscan_account_tokens, but it never explicitly contrasts itself with them, so no sibling-differentiation credit.

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 by the returned-data profile (multi-chain EVM holdings snapshot) and by the stated default chain set plus the operator-key condition for Base/Arbitrum/Polygon. There is no explicit 'use this when… use X instead' routing, and no mention of alternatives for pure-native or per-token queries.

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