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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the burden is low. The description still adds useful behavioral context: the default active-only filtering and the shape of returned records, which is more than the annotations convey.

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 tight sentences with no filler; the core purpose leads, the sibling routing follows, and the default filter closes. Every clause earns its place.

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?

An output schema exists, so return values need not be detailed further, and the description still summarizes what each record contains. Combined with the default-filter note and sibling routing, an agent has everything needed to call this 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?

Schema description coverage is only 50%: includeArchived is documented in the schema, but siteUrl is not. The description partially compensates by stating the default filter ('only active experiments are returned'), which clarifies includeArchived's semantics, and implies siteUrl via 'for a property'. It does not, however, specify the siteUrl format.

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 verb ('Lists') plus resource ('SEO experiments (split tests)') and enumerates the returned fields (control/variant URL groups, source, status, start date). It is clearly distinguishable from the sibling get_experiment_results, which it explicitly positions as the scoring counterpart.

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?

Names the alternative tool and the condition that selects it ('Use get_experiment_results to score one'), and states the default scoping behavior. It lacks explicit when-not guidance (e.g., what to do if no experiments exist), but the routing context is clear.

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