list_contacts

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

With no annotations, the description carries the full burden, but it only states the basic action. It does not disclose return format, ordering, pagination, whether deleted or blocked contacts are included, or any side effects. The read-only nature is implied but never 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?

A single, front-loaded phrase with no wasted wording. Every word contributes to meaning, and the description is appropriately sized for a tool with no parameters and no complex behavior.

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 list tool, the description is minimally sufficient, but it lacks any clarification of what 'contacts' means in context, what the returned data looks like, or how it relates to get_contact and get_user. It is adequate but leaves a few practical gaps for an agent.

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 has zero parameters, and the schema confirms this with 100% coverage. Since there is nothing to document, the description does not need to add parameter-level detail. Baseline 4 is appropriate for a parameterless tool.

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 states a specific verb ('List') and resource ('contacts'), clearly identifying the action. It distinguishes from get_contact by pluralizing 'all contacts', but it does not explicitly name or route to the sibling alternative for a single contact.

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 no guidance about when to use this tool instead of get_contact, get_user, or list_chats. There is no context for selecting this tool over alternatives, so the agent must infer from the name alone.

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