Assign a contact to a tag

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

Annotations already show this is not read-only and not destructive. The description adds useful behavioral details beyond that: the operation applies immediately and is idempotent—assigning an existing tag succeeds without duplicating it.

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 compact and well-structured: a one-line statement of purpose, followed by a relevant contrast to the bulk endpoint and a useful idempotency note. Every sentence earns its place.

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 simple single-contact tagging operation, the description covers the core behavior, immediate execution, and idempotency. No output schema exists, but the tool's effect is clear enough for an agent to invoke it correctly.

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%, with each UUID parameter minimally described. The description adds no additional parameter-level semantics, but the schema already provides enough labels for the agent to understand the three required identifiers.

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 action—'Assign a tag to a single contact'—with a clear verb and resource. It also distinguishes itself from the bulk endpoint, so an agent can tell this apart from sibling tools like reach_assignContactsToATagV1.

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 explicitly contrasts this tool with the bulk endpoint and notes that it is applied immediately rather than queued. This gives clear selection guidance for the single-contact case, though it does not name the sibling tool explicitly.

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