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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that: results are per-user filtered by tier and flags, and, most importantly, it warns that this tool must not be used as an existence check — a usage hazard the annotations cannot express.

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: the return value first, then the only legitimate trigger, then the anti-pattern. Every sentence earns its place and the most failure-prone guidance (don't use as preflight) is stated plainly rather than buried.

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, output-schema-less listing tool, the description covers what returns, how it is scoped, and the single misuse case that would otherwise cause agents to waste calls. Nothing further is needed to invoke it 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?

The tool takes zero parameters, so the baseline is 4. The description correctly adds no parameter detail because there is none to add, and the 'filtered by tier + flags' note clarifies that the output is implicitly scoped by the calling user rather than by an argument.

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 ('Returns the list of tools available to this user') and adds the scoping detail '(filtered by tier + flags)', so an agent knows exactly what comes back. It does not name or contrast itself with the siblings whoami or current_page_context, so it stops short of a 5.

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?

Explicitly gives both the trigger ('Use ONLY when the user asks "what can you do?"') and the exclusion ('NOT a preflight — never call it to check whether a capability exists before acting'), plus the alternative behavior ('just call the one that fits'). This is a textbook when/when-not/alternative statement.

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