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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuinely non-obvious operational facts beyond them: a $0.002 USDC cost per successful call, the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged. That pricing/payment model is exactly the kind of detail an agent needs before invoking a paid endpoint.

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 dense paragraph that front-loads what is returned, then restrictions, then price. Every sentence carries information, though the restriction and pricing clauses are run together in a way that is slightly hard to scan as separate concerns.

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 prose, and the description covers scope, asset, exclusions, and cost. The only mild gap is that it doesn't say what happens for unsupported chain pairs (error vs. empty result), which matters for a paid, rate-anchored call.

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% and the 'from' parameter even enumerates chain IDs, so the baseline is 3. The description earns above that by adding a constraint not in the schema: the pair must be one the Across limits API accepts, and the asset is fixed to USDC so no token parameter exists.

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 (Across bridge limits for USDC between two chains) and enumerates exactly the three values returned: max instant-fill, max deposit, min deposit. The 'Across only (not Stargate, Hop or CCTP)' clause separates it cleanly from sibling bridge/DeFi tools such as agent_intel_crosschain_gas_priority_fee and agent_intel_dex_depth_slippage_calculator.

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?

Explicit eligibility conditions are given: Across only, USDC only, and the chain pair must be one the Across limits API accepts. It does not name a concrete alternative tool to use instead for other bridges or tokens, but the exclusion list ('not Stargate, Hop or CCTP') conveys when this tool is the wrong choice.

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