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

Annotations already declare it is a non-destructive write with openWorldHint=false, so the safety profile is covered. The description adds genuine value beyond that by disclosing duplicate handling — existing entries keep their display name and aliases — and by naming the already_tracked response key, which matters since there is no output schema.

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?

Two sentences, both front-loaded and earning their place: the first states the action, the second states the edge-case behavior the agent would otherwise guess wrong about. No filler.

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 two-parameter write with no output schema, the definition covers the action and the one non-obvious outcome (already_tracked). It stops short of saying what happens to newly added domains, whether they are verified synchronously, or any quota implications of bulk adding.

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 description coverage is 100%, so both parameters are already documented, establishing the baseline of 3. The description adds no new detail about domain_id (e.g., that it must reference an existing tracked domain) or about the comma-separated format or limits on competitor_domains.

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 uses a specific verb and resource ('Add competitor domains to tracking'), which is enough to distinguish it from the read-only list-competitors and the delete/update siblings. It doesn't explicitly name those siblings, which keeps it short of a 5.

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 explains what happens when a domain is already tracked, which implicitly signals this is a batch-add rather than an edit path, but it never tells the agent when to prefer add-competitor over update-competitor or what precondition domain_id must satisfy. Usage is implied rather than stated.

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