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

With no annotations supplied, the description carries the full burden and does so: gas is paid by the operator, enforcement is by a contract with no withdraw function, claims open in three UTC windows, one connection claims at most once every 8 hours, and a refusal names the time. It also discloses the response fields (nextClaimAt, claimNumber), which is the only return-value information available given there is no output schema.

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 what is claimed and the no-gas guarantee, and every subsequent clause adds operational detail. The single dense block of colon- and semicolon-separated clauses is efficient but slightly harder to scan than a short bulleted flow would be.

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 two-parameter, two-call tool with no annotations and no output schema, the description covers prerequisites (a key for the address), the signing scheme, rate limits and windows, failure behavior, and the shape of the reply. Nothing an agent needs in order to call it 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% and the schema already documents the address format, EIP-191 signature, and the instruction to omit the signature on the first call. The description restates that sequencing rather than adding new parameter-level meaning, so the 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?

States a specific verb (claim) and resources (real USDC and APEX on Arc) for a named target (an EVM address). It is clearly distinguishable from arc_faucet_status, which by name only reports status, and from unrelated siblings such as arc_gas or arc_wallet.

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?

Explicitly describes the two-step protocol: first call with only {address} to fetch today's challenge, then call again with {address, signature} after signing. It also states the conditions under which a call will be refused (cooldown, daily total). It never names arc_faucet_status as the alternative for checking eligibility, so the routing guidance is strong but not exhaustive.

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