List Contacts

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is known. The description adds meaningful behavioral context: a 50-contact limit per call, pagination implication, and the presence of a handle useful for downstream operations. This goes beyond annotations without contradicting them.

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?

Two sentences, no filler. The first sentence immediately states the core function, the second provides a useful alternative. Every clause earns its place, making it highly concise and well-structured.

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?

With an output schema present, the description only needs to convey purpose, usage, and key constraints. It covers the pagination limit, the handle for dependent tools, and the sibling alternative. For a simple list tool, this is fully complete.

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 coverage is 100% and the schema itself documents count's range and default (default: 25, max: 50). The description mentions 'up to 50 per call,' which reinforces the limit but does not add significant new meaning beyond the schema. Baseline 3 is appropriate.

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 clearly states the action: 'Lists contacts from the user's address book.' It also distinguishes itself from the sibling tool search-contacts, which filters instead of paging, and implies the output format includes a handle for read-contact and delete-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?

Explicit guidance is provided: 'For a targeted lookup, search-contacts filters by name, email or phone instead of paging through the full list.' This directly tells the agent when to choose this tool versus an alternative, which is exactly what the dimension requires.

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