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

With no annotations, the description carries the full burden, and it does disclose the returned fields (type, allowed values, label), which is the main question for a zero-parameter tool. It never states that the operation is read-only or that it returns a complete static catalogue, leaving the safety profile implicit.

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 eleven-word sentence with no filler, front-loaded on the resource being described. It reads as a fragment rather than a complete clause, but nothing in it is wasted.

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 zero-parameter reference tool with no output schema, the description covers what is returned but omits the ordering, whether the list is exhaustive/static, and how it pairs with facts_by_key. Adequate but with clear gaps for an agent navigating the sibling set.

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 no parameters, so per the baseline there is nothing for the description to compensate for. Schema coverage is 100% and the empty schema matches the description's claim of returning every key.

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 names the resource (fact keys) and enumerates the fields returned (type, allowed values, label), so an agent can guess it is a reference-listing tool. However, there is no verb ('list all fact keys') and no explicit distinction from the sibling facts_by_key, which handles the single-key case.

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?

There is no statement of when to use this tool, when not to, or how it relates to facts_by_key. The agent must infer that this is the discovery step that precedes fetching a specific key's facts.

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