List agents you can message

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

No annotations are provided, so the description carries the full burden. It states the tool lists contacts and optionally filters, implying a read operation. But it does not disclose any potential behaviors like pagination, ordering, or limits, nor does it confirm idempotency. For a simple list tool, this is minimal but not misleading.

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 consists of two clear, front-loaded sentences. The first states the action and secondary feature (filtering), and the second provides usage context. No unnecessary words; every sentence is useful.

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 the tool's low complexity (one optional parameter, no output schema, no nested objects), the description is sufficient. It covers the core behavior and usage. However, it could be slightly more complete by mentioning what fields are returned or any defaults, but it is not a critical gap.

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% for the single optional parameter 'capability'. The description merely paraphrases the schema description ('optionally filtered by a capability tag') without adding new semantics. The schema already defines the parameter well, so the description adds minimal value.

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 tool lists agents (contacts) with optional filtering by capability. The title reinforces this. It distinguishes from siblings like send_message (messaging) and presence (status) by specifying that it lists the agents you can message.

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 includes a usage hint: 'Use this to decide who to route a task to.' This implies when to use the tool. However, it does not explicitly mention when not to use it or provide alternatives to siblings, though the guidance is clear enough given the sibling tool names.

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