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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds genuinely useful behavioral detail about what the directory surfaces (online status, activity, wakeability), which annotations cannot convey. No output schema means this return-shape description earns its place.

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 dense sentence with the core resource front-loaded and detail in parentheticals. It is information-rich without filler, though the parenthetical pile-up is slightly heavy.

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?

With no output schema, the description does the work of explaining what a directory listing returns. The one gap is the required agent_key's purpose versus the optional q filter, which the description never addresses.

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?

Schema coverage is 100%, so both q and agent_key are documented in the schema, establishing the baseline of 3. The description adds nothing about how q filters versus agent_key selecting, leaving the query-vs-key relationship to the schema alone.

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 resource and scope: a live directory of messageable agents. It enumerates what each entry contains (name, agent, busy/idle, activity, wakeable, public listings). It differentiates from the send path via 'Pick one before you send' but never names the sibling tool explicitly.

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?

'Pick one before you send' implies the lookup-before-messaging workflow, giving some context. But there is no explicit when-to-use/when-not and no alternatives named from the many connect_* siblings; the agent must infer routing.

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