Check a MoMo account is active

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

Annotations already declare readOnlyHint=true and openWorldHint=true; the description restates read-only and adds one genuinely new trait, that the call is free. It says nothing about the response shape, what an inactive/nonexistent number looks like, or error behavior, so it clears the lowered bar but does not enrich it much.

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?

Three short sentences, purpose first, then the pre-charge recommendation. Every sentence carries distinct information and nothing is padded.

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-only check with a fully documented schema, the definition is nearly complete. The only meaningful omission is what the tool returns (e.g. an active/inactive flag) and how an unknown number is surfaced, which the agent would have to discover at call time.

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 phoneNumber format (international, digits only, no +) is fully documented in the schema; the description adds no parameter guidance beyond it, 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 and resource ('Check whether a phone number is a usable MoMo account') and frames it against the charge flow, so it is clearly distinguishable from siblings like momo_request_to_pay and momo_payment_status.

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 an explicit pre-condition ('before trying to charge it', 'before any request to pay'), which is exactly the routing signal an agent needs to sequence this call ahead of momo_request_to_pay.

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