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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, so the safety profile is fully covered and the description doesn't contradict it. The description adds the functional context that factions serve as filter values, but says nothing about whether the set is static, how large it is, or whether it is exhaustive, which would help an agent decide between listing and querying.

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 sentence that front-loads the resource and immediately supplies the reason to call it. No filler, no restatement of the title.

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?

With an output schema present, the description need not explain return values, and a zero-parameter read tool needs little more. What is missing is the tie-in to the specific sibling (search_reference) that consumes these faction values, which would close the loop for an agent.

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 are zero parameters, so the baseline is 4 and there is no schema surface for the description to compensate for. The schema is an empty object and the description correctly describes a no-argument enumeration call.

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 opens with a specific verb and resource ('Lists the factions') and adds the role those results play ('narrow reference searches'), which separates it from list_units and list_reference. It never names a sibling explicitly, so differentiation is inferred from the subject matter rather than stated.

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 phrase 'can be used to narrow reference searches' implies the tool is called to obtain filter values before search_reference or list_reference, but that workflow is never spelled out and no alternative is named. Usage is implied rather than prescribed.

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