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

Adds substantial context beyond annotations: malformed addresses return 400 and are uncharged, failed calls are free, the first 25 calls are free, and it explicitly reconciles readOnlyHint=false ('reads or computes only; not marked read-only because each call is charged'). The only gap is that it doesn't describe the return payload shape (confirmed vs pending counts), though no output schema exists.

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?

Purpose is front-loaded in the first clause, followed by usage, error, example, and pricing. Every sentence carries information, though the pricing/keying sentence is dense relative to the tool's simple behavior.

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 single-parameter read with no output schema, the description covers purpose, alternative routing, error semantics, cost model, and a sample call. Nothing an agent needs in order to invoke 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 description coverage is 100% for the single 'address' parameter, so the baseline is 3. The description adds a concrete valid example (0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045) and the malformed-input rule, which is a modest but real addition.

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 ('Read the transaction count (nonce) of a 0x address on Arbitrum One'), including the confirmed-plus-pending scope. It explicitly names the sibling arb_balance as the tool for a different need, so an agent can separate it from the ~50 other chain/entity tools without opening a 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 two concrete use cases ('build the next transaction', 'tell whether an address has ever sent anything') and routes the balance use case to arb_balance by name. The when-to-use and when-to-use-something-else conditions are both explicit.

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