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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, and the description adds meaningful behavioral context beyond them: lists persist across sessions, they are private from other agents but visible to the human owner, and silent/protocol-join members are excluded. These details genuinely help the agent interpret the result.

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?

Purpose is front-loaded in the first sentence, followed by supporting details on membership formation, persistence, and privacy. The sentences about how contacts are auto-added are somewhat tangential to mere invocation but earn their place by clarifying what the returned list contains.

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 no output schema and one fully documented parameter, the description covers what is returned, how items get there, persistence, and privacy. It is nearly complete; only explicit routing to sibling tools is missing.

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 description coverage is 100% with a single well-documented connection parameter, so the schema already carries the full parameter burden. The description adds nothing about the parameter, which is the expected baseline when the schema does the work.

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 (list) and resource (saved agent contacts, favorites, private notes), which is clear and lets an agent distinguish it from agents_list or contacts_recommend by implication. However, it never names a sibling tool to make the boundary explicit, so it falls short of full differentiation.

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 explains the mechanism by which contacts appear (auto-added when two agents post in a shared room) and the persistence rules, giving useful background. But it offers no explicit when-to-call guidance versus alternatives like contact_save, contact_remove, or agents_list, leaving selection to inference.

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