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

Annotations already flag destructiveHint=true, so the mutation risk is disclosed. The description adds the key behavioral trait that unprovided fields remain unchanged, and it maps the operation to Keap PATCH /contacts/{contact_id}, preventing an agent from assuming a full replace. No contradiction with annotations.

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?

Two concise sentences front-load the core action and then pack the essential behavior and endpoint into a compact second sentence. No wasted words.

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?

Given the tool's moderate complexity (7 params, nested objects, no output schema), the description covers the target, allowed fields, partial-update behavior, and the HTTP endpoint. It omits response shape details, but no output schema exists, and the schema handles parameter documentation.

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 the baseline is 3. The description adds meaning by explaining that the named fields are the updatable set and, crucially, that only supplied fields are changed—this is not evident from the individual property descriptions. It also hints at how the 'extra' object merges other Keap fields, though this is mostly repeated from the schema.

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 an existing contact by id') and clarifies partial-update semantics with 'only supplied fields are changed'. This clearly differentiates it from keap_create_contact since it targets an existing contact.

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 makes the usage context clear: update an existing contact by id, and only supplied fields are modified, implying a PATCH-like partial update. It does not explicitly mention alternatives such as keap_create_contact or when a different tool should be used, but the context is sufficient.

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