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

With no annotations provided, the description carries the behavioral disclosure burden. It discloses that this is an update operation, specifies the connection target behavior, and states that it 'Returns the updated domain.' It also mentions cost. However, it does not discuss permissions, error cases, or side effects on existing domain settings, which would be expected for a mutation tool without annotation coverage.

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 five short sentences, each with a clear purpose: action, prerequisite, targeting instruction, return value, and cost. It is front-loaded with the core verb-resource statement, and no filler or redundant text is present.

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 an output schema exists and the tool has four parameters, the description covers the essential operational context: what it does, prerequisite calls, connection targeting, return value, and cost. It could be more complete by addressing error scenarios or when to choose this tool over alternatives, but it is otherwise sufficient 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?

The input schema covers all parameters with descriptions, giving a baseline of 3. The description adds value by explaining the clerk_instance_id parameter's role in targeting a connection and instructing to call clerk.get_connected_accounts first, which clarifies provenance. This goes slightly beyond the schema's own parameter descriptions.

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 opens with a specific verb and resource: 'Update a custom domain on a connected Clerk instance.' This clearly establishes the tool's function and distinguishes it from related domain operations like add_domain or delete_domain. The subsequent prerequisite and target-selection details further clarify scope.

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 provides clear context for use: 'Call clerk.get_connected_accounts first' and explains how to target a connection via clerk_instance_id or default. However, it does not explicitly contrast this tool with alternatives like clerk.update_organization_domain or specify when not to use it, so it stops short of full guidance.

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