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

Reveals important behaviors beyond the annotations: PATCH-like partial update semantics, sentinel values for removal, and the critical warning that owner_id refers to an employees.id, not an auth user id. This is exactly the kind of behavioral context agents need.

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?

Four dense sentences with no filler. The core action is front-loaded, followed by partial-update semantics, removal behavior, and id/list constraints. Each sentence contributes a distinct operational rule.

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 17-parameter mutation with no output schema, the description covers the non-obvious essentials: partial updates, removal sentinels, the owner_id domain distinction, and list_id lookup scope. Minor gaps remain, such as how to clear ordinary string fields, but the critical context for correct invocation is present.

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?

With schema description coverage at only 35%, the description compensates for the most ambiguous parameters: list_id can be a name or id and is workspace-scoped, owner_id is an employee id, and is_collaborator: false removes the mark. Remaining fields are reasonably self-explanatory by name, and the global partial-update rule applies to all.

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 precise verb and resource: 'Update fields on a contact', and enumerates the contact-specific field categories (address, extra phone numbers, CVR/VAT, collaborator mark, list). This clearly distinguishes it from sibling update tools like crm_update_deal or crm_update_lead.

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?

Provides strong operational context: it explains that only passed fields change, and gives specific removal semantics for list_id and is_collaborator. It does not explicitly name alternative tools, but the partial-update guidance makes the when and how clear.

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