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

With no annotations, the description carries the full burden and does so well: it discloses no wallet/signature requirement, that it is served entirely from cached rows at zero catalogue cost, and that unfetched pictures or counts return null rather than triggering a fetch. That null-on-stale behavior is a non-obvious trait an agent would otherwise misread as an error.

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?

Front-loaded with the payload shape, then endpoint, then auth, then caching semantics, then the sibling routing rule — a sensible order with no dead sentences. The shop/shelf metaphor adds a little verbal overhead but does reinforce the 'one read vs. walking down' tradeoff.

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 read with no output schema, the description supplies the return shape (three nested levels), the freshness contract, the auth posture, and the alternative tool. There is essentially nothing else an agent needs before calling it.

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; there is nothing for the description to disambiguate. The description's implicit point that no filtering arguments exist is consistent with the empty schema.

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 exactly what comes back — departments, the groups under them, and the links under those — plus the endpoint (GET /api/agent/browse/directory). The closing sentence names the sibling tool it replaces (get_category), so an agent can distinguish it without inspecting either schema.

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?

Gives an explicit selection rule: 'Prefer this over repeated get_category calls when you are still deciding where to look.' That names both the alternative and the condition that selects it, which is exactly the routing guidance an agent needs among the seven siblings.

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