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

With no annotations, the description carries the full behavioral disclosure burden. It explicitly discloses that registration is not activation, that the host must be unique platform-wide, and that only one host is allowed per organization. It does not cover idempotency, errors, or response shape, but the essential operational constraints are well stated.

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, but it repeats 'One per organization' twice and restates 'registering never activates it' as 'Registering does not activate'. This redundancy prevents it from being fully concise.

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 two-parameter create operation with no output schema, the description gives the functional sequence and constraints an agent needs: register, publish CNAME, then verify. It does not describe the return value, but that is a minor gap given how simple this tool is.

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 both parameters. The description adds useful meaning by tying `domain` to message-link serving and by adding uniqueness and one-per-organization constraints. It does little for `organization_id`, but the added domain context exceeds the baseline.

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 action and resource: 'Register the host that will serve this organization's message links'. It clearly distinguishes the tool from verification by explicitly saying registration never activates and pointing to `verify` as a separate step. The tracking-domain scope also separates it from sibling domain tools.

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?

Gives clear operational context: one per organization, unique across the platform, and registration alone does not activate the host. The workflow is implied strongly — publish the CNAME then call `verify` — though it does not explicitly name alternative tools or state when not to use this one.

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