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

Annotations only declare destructiveHint=true; the description goes well beyond that by disclosing that tags/phones/emails REPLACE existing lists, that contacted=true pauses action plans, and that source/sourceUrl are immutable post-creation. These are exactly the destructive side effects an agent must know before invoking, and they are consistent with the destructiveHint annotation.

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?

Dense and front-loaded: the cautions about replacement and immutability come before the API endpoint reference. Every clause carries actionable signal with 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?

For a 19-parameter mutation tool with no output schema, the description covers the highest-risk behaviors (list replacement, action-plan pausing, immutable fields) that an agent most needs. It falls short only in not touching the remaining assignable/price/address parameters, which is a minor gap given the destructive semantics are covered.

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 low (32%), so the description must compensate. It does add crucial semantics for tags, mergeTags, phones, emails, and contacted, but leaves other significant parameters (price, stage, addresses, customFields, assigned* fields) unexplained beyond the schema, so the gap is only partially closed.

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 and resource ("Update a contact's fields") that is easily distinguished from read siblings like fub_get_person or fub_search_people. It does not explicitly name alternatives or contrast scope with fub_update_deal/fub_update_task, but the purpose is 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 explains behavior (what gets replaced, what is immutable) but never states when to use this tool versus alternatives such as fub_search_people to locate a record first, or fub_update_deal for related data. No prerequisites or exclusions are given.

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