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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuinely non-obvious behavior: the search spans the whole account including records this user cannot see, and the response includes assignment. It doesn't state what happens when nothing matches, a minor gap.

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, front-loaded with the core behavior, then the usage cue, then the API reference. No filler.

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 by stating the result includes assignment and covers invisibly-scoped records. It leaves the no-match case and whether email/phone can be combined unstated, which is a small but real gap for a duplicate-check 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% and both params are optional with clear descriptions, so the schema does the heavy lifting (baseline 3). The description confirms email/phone are the lookup keys but adds no format, matching, or combination semantics beyond that.

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?

Specific verb (check duplicate) plus resource (person/contact) and the exact lookup keys (email or phone). The scope note 'anywhere in the account (even ones this user cannot see)' distinguishes it from fub_get_person and fub_search_people without the agent needing to open either 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?

Explicit trigger: 'Use before adding a lead.' That gives a clear when-to-use condition. It does not name search_people/get_person as the alternatives for non-duplicate-check lookups, so it stops short of full routing guidance.

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