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

The description adds meaningful behavior beyond the annotations: case-insensitive dedupe by email, merging of fields and tags, company creation/reuse, and the required write_crm scope. It does not clarify whether omitted standard fields are left unchanged or cleared during an update, which is a notable behavioral gap for an upsert.

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?

The description is short and front-loaded, starting with the create-or-update behavior and then covering merge, company handling, and scope in four efficient sentences. Every sentence adds value.

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 an 11-parameter upsert tool with full schema descriptions and rich annotations, the description provides enough behavioral context to invoke it correctly. It covers the core upsert semantics, merge behavior, company side effect, and authorization requirement; return values need not be described because there is no output schema.

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 coverage is 100%, so the schema already documents all 11 parameters and establishes a baseline of 3. The description still adds useful semantic detail for key parameters: email as the case-insensitive dedupe key, merge behavior for fields and tags, and company creation/reuse from company_domain or company_name.

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?

The description states a specific create-or-update operation for a contact and identifies the email-based match key, merge behavior, and company handling. It is clear what the tool does, though it does not explicitly contrast itself with the sibling update_contact tool.

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?

It clearly explains that the tool creates a contact or updates an existing one matched by email, including case-insensitive matching and merge semantics. It does not explicitly state when to prefer this over update_contact or when not to use it, so alternatives are left implicit.

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