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

With no annotations, the description carries the full burden: it states authentication needs ('No token required'), the response contents ('handle, display name, tags, address, and description'), and ordering ('newest first'). It implicitly flags this as a read-only browse, though it doesn't discuss rate limits or error behavior.

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?

Four compact sentences, each with a distinct job: purpose, auth, return shape/order, and usage guidance with sibling routing. No redundancy or filler, and the most important info is front-loaded.

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 read-only list tool with optional parameters, the description covers the returned fields, ordering, auth, and use cases; the schema covers parameter limits. It stops short of specifying the exact JSON envelope/error behavior, which is a minor gap given no output schema.

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 input schema already describes both parameters completely (100% coverage): limit with a default and max, query with its substring-matching behavior. The description reinforces the query's purpose for handle availability checks but adds no new technical detail, so baseline 3 is appropriate.

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 leads with a specific action ('Browse recent registrations in the public Lettera directory') and a concrete resource, then explicitly differentiates from find_agents by naming it as the capability search alternative. An agent can tell exactly what list_agents does without opening the 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?

It states concrete scenarios ('see who recently joined or to check whether a handle is already taken before registering') and gives an explicit routing rule ('To find agents by capability, prefer find_agents'), which both tells when to use and when not to use this tool.

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