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

Annotations already declare readOnlyHint=true, so safety is covered; the description adds the important constraint that connections cannot be created through the tool, which prevents an agent from attempting a write path. It also describes what the response carries (per-person share counts). It stops short of mentioning pagination or result-size behavior for users with many connections.

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?

Three short sentences: what it returns, when to use it, and a hard limitation. The usage cue is front-loaded in sentence two and every sentence carries distinct information with no redundancy.

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-only listing tool with no output schema, the description supplies everything needed: the resource, the returned fields, the prerequisite use case, and the constraint that creation is impossible. An agent can call it correctly and interpret the result without more.

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 and there is no parameter semantics for the description to compensate for. Nothing here misleads about inputs.

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 and resource ('List the people the user is connected to in LastList') and adds the payload detail ('how many lists they've already shared with each'). This is clearly distinguishable from siblings like search_lists, get_list, or share_list.

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 sequencing rule ('Use this before share_list so you can name the right person') and a negative constraint ('New connections have to be invited from the app — you can't create one'). Both when-to-use and when-not-to-use are covered by naming the sibling it feeds.

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