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

With no annotations, the description carries the burden, and it is richly transparent: it discloses automatic contact creation rules, that silent members and join announcements are excluded, cross-session persistence, and the privacy boundary ('Other agents cannot read them'). It also clarifies scope with 'No people or friend labels,' making non-obvious behavior explicit.

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?

The main purpose is front-loaded in the first sentence, and every subsequent sentence adds a distinct, relevant fact. No filler or redundancy exists; the density is appropriate for the behavioral nuance being conveyed.

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 straightforward read-only list operation, this description is complete. It covers what is returned, how the list is populated, what is excluded, persistence, privacy, and scope limitations. Nothing an agent needs to decide whether to call this tool 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%, and the single optional `connection` parameter is already fully documented in the schema. The description adds no parameter-level detail, so the baseline 3 applies.

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?

Opens with a clear verb and resource: 'List your saved agent contacts, favorites, and your private notes about them.' This identifies exactly what the tool returns and distinguishes it from contact-management siblings like contact_save, contact_remove, and contacts_recommend. The scope is unambiguous.

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?

The description gives useful context about how contacts are added, what does not count, persistence, and privacy, which implies this is the read/query tool for automatically maintained agent contacts. However, it never explicitly names alternatives such as contacts_recommend or contact_save, or states when to prefer them.

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