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

Annotations already declare readOnly/destructive/openWorld/idempotent, and the description adds genuinely new behavioral facts: per-call cost ($0.01 via x402 USDC or card key), first 25 free, failed calls free, and that repeats are charged — which concretely explains the idempotentHint=false. It also discloses result caps (up to 100 logs) and the block-scan ceiling.

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 purpose, then scope, then return shape, then routing, then pricing — a logical order in one dense paragraph with no filler sentences. It is on the long side and the pricing/credits clause competes with the core usage guidance, but each element carries information.

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?

With no output schema, the description correctly describes the return payload (up to 100 logs with block, transaction hash, topics) and covers cost, filters, and limits. It does not explain what happens when a block range would yield more than 100 logs (truncation vs. error vs. pagination), which is the one operational detail an agent might need.

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 goes slightly further by clarifying topic0 is a 32-byte event signature hash and by supplying a concrete address example. It largely restates the blocks range and default already in the schema, so it stops short of a 5.

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 ("Recent contract event logs on Unichain"), anchors it to the underlying RPC method (eth_getLogs), and explicitly distinguishes itself from the sibling unichain_receipt. An agent can tell this apart from unichain_tx or unichain_receipt without opening any schema.

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 clear when-to-use ("watch transfers or contract events") and an explicit when-not with the alternative named ("for one transaction's outcome use unichain_receipt"). The one gap is that recommending transfer-watching without mentioning the sibling unichain_token_transfers leaves a routing ambiguity for that specific use case.

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