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

No annotations exist, so the description carries the burden, and it does disclose the two traits an agent most needs: the cost ($0.003 per call) and the payment path (USDC over x402), plus the data source (prefix allocation). It stops short of stating failure behavior for invalid or unassigned prefixes and whether the lookup is offline or live, which are the remaining gaps.

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?

Two short sentences with no waste: price and payment rail front-loaded, then the operation and its outputs. Every clause carries information the agent would otherwise have to guess.

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 one-parameter lookup with no output schema, the description names the return fields and the cost model, which is close to sufficient. It could be stronger by noting what the response looks like when the prefix is unassigned or the number malformed.

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% with a single required parameter, so the baseline is 3. The description adds genuine value beyond the schema's lone example by naming the three accepted formats (local, +234, 234), telling the agent it need not pre-normalise.

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 (normalise a Nigerian phone number) and enumerates the returned fields: E.164, line type, and network. The subject matter (phone-number normalisation) is clearly distinct from the chain_* tools and from ng_bank_validate / ng_identity_format without needing to open 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?

Accepted input forms (local, +234, 234) are given, which tells the agent the tool can be called directly on any Nigerian number format. However, there is no explicit guidance on when to prefer this over ng_bank_validate or ng_identity_format, and no mention of what to do with non-Nigerian numbers.

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