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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely new context: it is Moda's own published check, what verdict values can come back, what gets matched, and that moda_rules contains Moda's published wording on what it never asks for.

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-loaded with the 'Use when' trigger, then value format, then return shape, then exclusion. Dense but well ordered; the only slight redundancy is restating the accepted value types already in the schema.

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?

There is no output schema, and the description compensates fully by listing the three verdict values, what match data is returned, a human-readable summary field, and the moda_rules field. For a one-parameter read-only check, nothing an agent needs to call or interpret it is missing.

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 description coverage is 100% and the parameter already enumerates the accepted value types, so the schema carries the load. The description adds only the 'exactly one of' constraint, which is useful but marginal, so the baseline of 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+resource (a scam check on a Moda contact) and defines scope precisely: contact via person, number, email, or business. The final sentence explicitly excludes Facebook group and post links, which are covered by the sibling check_facebook_group_link, so the tool is distinguishable without opening the 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?

The opening clause gives a clear triggering situation ('someone was contacted by...' or 'wants to know if one is real'), and the last sentence gives an explicit exclusion for group/post links. It stops short of naming the sibling tool that should be used instead, so the agent must infer the routing.

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