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

With no annotations, the description carries the full burden. It conveys that this is an observational read ('observation', 'seen') and describes the response content, but it does not disclose failure behavior, freshness limits, or whether any external network call is made.

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 a single dense sentence with no filler. It front-loads the core purpose and then lists the response components, though it could be slightly clearer with an explicit leading verb like 'Returns'.

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 simple one-parameter lookup with no output schema, the description covers purpose, parameter semantics, and return content. It lacks edge-case behavior (e.g., missing observations, exact URL normalization) but is otherwise minimally sufficient.

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 0%, so the description must compensate. It adds meaningful semantics to the url parameter by specifying 'exact resource URL (path and query included)', which is valuable beyond the schema's bare string type.

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 names the specific resource ('payability observation'), the scope ('one exact resource URL'), and the return contents (verdict meaning, remediation, per-network options). This distinguishes it from siblings like catalogue_stats or x401_status, which cover different concerns.

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 context is clear: use this when you need the latest payability observation for a specific exact URL. It does not explicitly name alternatives or give when-not-to-use guidance, but the exact-URL scope implies the applicable situation.

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