Export an event window for the Rerun viewer

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

Annotations already declare idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it requires a separate viewer, does not launch the viewer, does not produce camera/3D replay, and instructs to inspect topic schemas and use source timestamps in seconds. This goes beyond the 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?

Three sentences with no filler. The core action and return value are front-loaded, followed by usage conditions and exclusions. 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?

The description covers purpose, prerequisites, exclusions, and return value. With an output schema present, the return value doesn't need full enumeration. The only minor gap is that it doesn't explain the 'signals' parameter's relationship to 'topics' in detail, but the scalar time series framing and output schema compensate.

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 description coverage is 0%, so the description must compensate. It explains the core parameters conceptually: 'selected time window' maps to start_seconds/end_seconds, 'scalar time series' maps to topics/signals, and 'returns its path' maps to path. It doesn't enumerate each parameter, but it gives enough semantic framing for an agent to understand the tool's purpose. The 'use source timestamps in seconds' note adds crucial unit semantics for the time parameters.

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 ('Write'), a resource ('selected time window as scalar time series in a Rerun .rrd recording'), and the return value ('path, signals, and an opening command'). It also distinguishes itself from other exporters by naming the Rerun format and explicitly noting it does not produce camera/3D replay.

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 explicit when-to-use guidance ('Choose this when the user requests Rerun'), prerequisites ('Requires rerun-sdk (uv sync --group viz) and a separate viewer'), and exclusions ('does not produce camera or 3D scene replay and does not launch the viewer'). This clearly routes an agent away from sibling exporters like export_for_plotjuggler or export_for_lichtblick.

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