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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds genuinely new behavioral context: the cost model (free), the authorization prerequisite (plan or positive prepaid balance), and expected latency (first data in 24-72h). It omits what happens on a duplicate request for an already-monitored domain, which is the one behavior an agent would still want.

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?

Three short sentences, front-loaded with the action, then the gating condition, then the timing expectation. Each sentence adds information, though "Free" partially duplicates the title's "(free, gated)" and could be trimmed.

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 one-parameter write tool with no output schema, the description covers the essentials: what happens, what is required to succeed, and how long results take. Annotations already supply the mutation/idempotency profile. The only material gap is duplicate-request behavior for an already-tracked domain.

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?

There is a single parameter with 100% schema description coverage ("Domain to start monitoring"), so the schema already carries the load. The description adds no format guidance beyond it, such as whether subdomains, paths, or full URLs are accepted. Baseline 3 is appropriate when the schema documents the only parameter.

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 verb and resource: "Ask RivalSweeper to add a domain to monitoring." An agent can immediately tell this is a write/onboarding action rather than a read, distinguishing it from siblings like list_my_tracked_brands or check_brand_data_coverage. It stops short of naming a sibling it should be preferred over (e.g., request_missing_data_signal), so it is clear but not fully differentiated.

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 supplies real selection context: the tool is free but gated behind an active plan or a developer account with a positive prepaid balance, which tells the agent when the call will actually succeed. It does not, however, state when-not to use it or which alternative handles related needs, so it is clear context without exclusions.

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