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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds real context beyond them — that results are scoped to the authenticated agent tier / current key, i.e. auth-dependent output — but says nothing about result size, caching, or whether the catalog changes over time.

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 with no filler, front-loading the action and immediately qualifying it with scope. Every clause carries meaning.

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?

A zero-parameter, read-only tool with an output schema and full annotation coverage needs little prose, and the description correctly explains the key-scoped behavior and the return category (endpoint catalog). The only gap is routing guidance versus the many discover_* siblings.

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, so there is nothing for the description to disambiguate; baseline 4 applies. The schema is an empty object and needs no compensation.

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 and resource ("List protocol capabilities") with a clear scope qualifier ("available at the authenticated agent tier"). The parenthetical "endpoint catalog for the current key" usefully pins down what the resource actually is, though it does not explicitly contrast with the kellian_discover_* siblings.

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?

No explicit "use this when" statement or named alternative. Usage is only implied: the tool is framed as an endpoint catalog for the current key, so an agent can infer it is for introspection of what the key permits, but nothing tells it when to prefer a discover_* tool instead.

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