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

readOnlyHint already declares a safe read. Beyond that, the description discloses a non-obvious behavioral trait: it sees contacts the user cannot otherwise see, and returns assignment information. This is meaningful context the annotations don't carry.

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 tight sentences; the core behavior and the usage trigger are front-loaded with no wasted wording.

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 read-only lookup with no output schema, the description conveys the key return concept (existence plus assignment). It could say more about the response shape (e.g. whether multiple matches are returned), but it is essentially complete for calling the tool.

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%, so both email and phone are fully documented in the schema. The description adds no format or syntax detail beyond restating the email-or-phone lookup, so 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 (check) and resource (contact/email/phone) and clarifies scope: it searches the entire account, including records this user cannot see. This implicitly distinguishes it from search/get siblings, though it never names them explicitly.

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?

'Use before adding a lead' gives a clear trigger context. It doesn't spell out exclusions or point to alternatives like fub_search_people or fub_get_person, but the when-to-use guidance is concrete.

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