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

No annotations are supplied, so the description carries the full behavioral burden, yet it only discloses the returned fields (ids + verification states). It says nothing about ordering, pagination, whether the full set is returned at once, or whether any permission is required to read verification states — meaningful gaps for a zero-param index endpoint.

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?

A single front-loaded sentence with no wasted words, which is the right size for a trivial index tool. The parenthetical "(marriageuk)" and the "+" shorthand are slightly cryptic but do not impede comprehension.

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 no-param list tool with no output schema, the description covers what comes back at a high level, which is the essential piece. It falls short on ordering, completeness of the result set, and the follow-up call (get_fact), which an agent needs to actually use the output.

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 tool takes zero parameters and the schema is a bare empty object, so there is nothing for the description to disambiguate. Baseline 4 applies; the description adds no misleading parameter claims.

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?

Specific verb ("List") plus the exact fields returned ("fact ids + verification states") and the domain qualifier ("marriageuk"). It is clear this is an enumeration tool, though it does not explicitly contrast itself with sibling marriageuk_get_fact, so an agent must infer that one returns a single fact rather than the index.

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 gives no when-to-use or when-not-to-use guidance, no mention of a prerequisite discovery step, and does not name marriageuk_get_fact or marriageuk_changes as alternatives. Only the bare verb "List" implies it is the entry point for browsing, which is left entirely to inference.

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