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

The description claims idempotency ('Idempotent transactional messages') and details 24-hour replay semantics, but the annotation idempotentHint is explicitly false. This is a direct contradiction. The description does add useful behavioral context (channel fallback, honest failure, cost, latency, execution model), but the contradiction mandates a score of 1.

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?

The description is well-organized with labeled sections and front-loaded intent, making it easy to scan. It repeats 'Do not use for marketing' in both WHEN TO USE and WHEN NOT TO USE, and the example/schema mismatch detracts, but overall structure is strong.

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?

The description includes cost, latency, execution mode, and points to get_outcome for retrieving results, which helps compensate for the lack of an output schema. However, the idempotency contradiction and the mismatch between the example and the input schema leave important gaps in an agent's ability to call it correctly.

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?

With only 40% schema description coverage, the description needed to compensate, but its example uses recipient.id_type/id_value while the schema requires recipient.phone_or_email, and data.business_name while the schema example mentions smb_name. These conflicting field names mislead rather than clarify, so the description adds little positive value beyond the schema.

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?

The description clearly identifies the tool's scope by enumerating concrete message types (OTPs, booking confirmations, payment receipts, cancellation notices) and distinguishes it from marketing/conversational messaging. It relies somewhat on the tool name for the verb, but the example query and 'MUST be delivered reliably' phrasing make the purpose unambiguous.

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?

The description explicitly provides WHEN TO USE and WHEN NOT TO USE sections, stating when it is appropriate ('MUST be delivered reliably') and when it should not be used (marketing, promotional, conversational). This clearly routes the agent away from siblings like send_message.

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