presence

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

Description implies a read-only operation ('list'), but annotations set readOnlyHint to false, creating a contradiction. The tool may have side effects not disclosed, violating the requirement for consistency.

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 with no wasted words; first states action and parameter, second gives usage context. Perfectly efficient.

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 one optional parameter and an output schema, the description provides sufficient behavioral context, including threshold, self-exclusion, and use case. No gaps.

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?

Single parameter 'idle_threshold_min' is explained in description as 'heartbeats within threshold (default 5 min)', adding meaning beyond schema, though type constraints are not elaborated.

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?

Description clearly states it lists concurrent Claude sessions with heartbeats within a threshold, excludes self, and distinguishes from siblings by specifying 'concurrent sessions' and 'excludes self', which differentiates it from tools like 'whoami' or 'peers'.

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?

Provides context for use ('before making changes') but does not explicitly state when not to use or suggest alternatives. Clear enough for an agent to understand typical usage scenario.

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