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

Goes well beyond the readOnly/openWorld annotations: it discloses a per-call cost ($0.002 USDC), the payment rails (x402 on Base, Solana or Arc), and that failed calls are not charged — critical behavioral facts for an agent deciding whether to invoke. It also bounds the history output (up to 60 points).

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-loaded with the resource and source, then the field list, then a separate pricing sentence — no filler. The single dense first sentence packs many clauses, which is slightly heavy to parse but each clause carries a distinct fact.

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?

For a read-only, 2-parameter tool with an output schema and annotations already in place, the description supplies the remaining gaps: data source coverage, what dimensions the payload breaks down by, history limits, and payment/cost behavior. Nothing an agent needs to decide and call correctly 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%, so the schema already documents both parameters and a 3 is the baseline. The description adds real meaning beyond it: 'period' is described as triggering the value history chart and is capped at 60 points, which explains the consequence of setting it rather than just the allowed values.

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 resource (on-chain wallet portfolio and performance) with a named data source and scope (Zerion, 40+ EVM chains and Solana), plus an enumeration of what is returned (total value, position-type split, chain split, 1-day change, lifetime PnL, history chart). An agent can distinguish this from siblings like crypto_debank_wallet_portfolio or crypto_zapper_token_balances by the source and the PnL/history coverage.

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: an agent can infer this is for 'wallet portfolio + performance' queries, and the phrase 'with a period, the value history chart' signals a conditional mode. However there are no explicit when-not-to-use rules and no named alternatives (e.g., debank_wallet_portfolio, zapper_token_balances), which matters given a large overlapping sibling set.

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