list_contacts

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

With no annotations provided, the description must disclose behavioral traits. It states the returned fields and that there is no ordering, which is helpful. However, it does not mention potential limitations (e.g., pagination, rate limits, whether blocked contacts are included), so it is adequate but not thorough.

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 description is two sentences, no extraneous words, and clearly front-loads the main action. Every sentence adds value.

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?

Given no output schema and no annotations, the description leaves some gaps: it does not specify whether the list includes all contacts (e.g., blocked?) or how the response is structured. For a simple read tool, it is adequate but could benefit from mentioning format or limitations.

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 has zero parameters, and schema description coverage is 100%, so the description does not need to add parameter meaning. Baseline for 0 parameters is 4.

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 uses a specific verb (List), identifies the resource (authenticated user's full LINE friend list), and specifies return fields (mid + displayName). It distinguishes from siblings like find_contact or add_friend by implying this is a complete listing without filtering or modification.

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 clarifies what to expect (full list, as-is, no ranking or ordering), which helps the agent know when this tool is appropriate. However, it does not explicitly state when to use this over alternatives like search_contacts or list_excluded_chats, leaving some ambiguity.

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