pi_sessions

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

With no annotations provided, the description carries the behavioral burden. It clearly discloses listing order, the working directory field, and the inclusion of running, finished, and timed-out sessions. The only minor gap is that it doesn't state return format or error behavior, but for a listing tool the disclosed scope and status coverage are strong.

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?

Three sentences with no filler. The first sentence delivers the core behavior and result fields, the second gives the primary use case, and the third handles sibling differentiation. Every sentence earns its place.

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 parameterless list tool with no output schema, the description is complete enough: it states scope, ordering, covered statuses, a concrete usage purpose, and the related alternative for in-progress sessions. Nothing essential for correct invocation is missing.

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, which is the baseline case for a 4. The description correctly focuses on what the return value contains (all sessions, working directory, ordering) rather than parameter details, which are not applicable.

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') with a clear resource ('pi sessions'), and adds distinguishing details: 'started through this server, newest first, with their working directory'. It also covers inclusion criteria (running, finished, timed out) and explicitly differentiates from the sibling pi_running, so an agent can select it correctly.

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 states exactly when to use the tool: 'Use it to recover an id for pi_reply.' It also gives an explicit exclusion: 'For turns still executing (pi_send targets), use pi_running.' This directs the agent to the right sibling without ambiguity.

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