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

Goes well beyond the annotations by disclosing error behavior (400 on malformed address), cost model ($0.01/call via x402 or card key, first 25 free, failed calls free), and the fact that repeated calls are charged, which explains the otherwise puzzling idempotentHint=false. The only gap is that it doesn't say what a successful payload looks like structurally, though the confirmed/pending split is mentioned.

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 the core definition and the sibling routing before the operational detail, so an agent can stop reading early. It is on the long side and 'Reads or computes only and changes nothing' partially restates the readOnlyHint annotation, but no sentence is pure filler.

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 tool with no output schema, the description covers purpose, sibling routing, error case, and billing, which is enough to call correctly. Return shape (field names for confirmed vs pending nonce) is left implicit, which is the only real shortfall.

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% for the single 'address' parameter, so the baseline is 3. The description adds a valid example address and states the rejection behavior for malformed input, but adds no format constraints beyond what the schema already implies.

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 Sonic') plus the scope ('both confirmed and including pending transactions'). It also explicitly separates itself from the nearest sibling by pointing to sonic_balance, so an agent can distinguish it without opening either 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?

Names two concrete use cases ('build the next transaction', 'tell whether an address has ever sent anything') and an explicit alternative for the adjacent need ('for its balance use sonic_balance'). The malformed-address condition is also called out, which tells the agent what input would fail.

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