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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the description doesn't need to restate those. The description adds valuable behavioral context: the effect is restricting widget token usage to specified domains, subdomains are included, and an empty list disables restriction (allowing any site). This goes beyond the annotations by explaining the security implication and the localhost development use case. It doesn't mention rate limits or auth, but for this simple configuration tool, the added context is sufficient.

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 three sentences, each earning its place: the first states the core function and security rationale, the second gives the usage pattern with an example, and the third covers the empty-list edge case. It is front-loaded with the primary purpose and uses compact, clear language without redundancy.

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 single-parameter configuration tool with no output schema, the description is nearly complete. It covers what the tool does, how to use it, the parameter format, and the important edge case. The only minor omission is not describing the return value or success/failure behavior, but since there is no output schema and the tool is a simple setter, this is a small gap. The idempotentHint annotation also covers the repeatability aspect.

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 0%, so the description carries the full burden of explaining the 'domains' parameter. It does this well: it explains the parameter is an array of domain strings, provides a concrete example (['example.com', 'example.vercel.app']), clarifies subdomains are included, and explains the empty-list behavior. The only minor gap is not specifying the exact string format (e.g., no protocol, no wildcard support), but the example makes this reasonably clear.

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 clearly states the tool's purpose: restricting the chat widget to the site's domains, including subdomains, to prevent token misuse on other sites. It uses a specific verb ('Restricts') and resource ('chat widget'), and the domain restriction purpose is unambiguous. It distinguishes itself from siblings by focusing on domain allowlisting, which is unique among the listed 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?

The description provides explicit usage guidance: send production and staging domains, with an example format, and send an empty list to allow any site (useful for localhost development). This tells the agent exactly when and how to use the tool, including the edge case of empty list. It doesn't need to name alternatives because the domain restriction function is unique among siblings, but the guidance is still explicit and actionable.

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