wakatime_session_duration

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

With no annotations provided, the description carries the full burden. It does add useful context: it computes and subtracts consumed ranges, returns a formatted summary, and does not expose raw heartbeats. However, it does not explicitly state whether the operation is read-only or if any data is mutated, nor does it clarify what 'consumed ranges' are or how they are sourced. This leaves some ambiguity about side effects.

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 is two concise sentences, front-loaded with the main verb 'Fetch' and a clear resource. It includes a useful output example without unnecessary fluff. Every word 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 tool is moderately simple with only three parameters and no output schema. The description provides the expected output format and key behavioral notes (no raw heartbeats). However, it lacks explicit usage guidance, does not explain the concept of 'consumed ranges', and offers no mention of prerequisites like authentication. This is adequate but leaves gaps that an agent must infer.

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 input schema already has 100% description coverage for all three parameters (project, since, branch), so the description does not need to compensate. The description adds no extra parameter-specific meaning beyond what the schema provides, making the schema the primary source of parameter semantics. It aligns with the baseline of 3.

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's function: fetching heartbeats, computing per-file coding time, and subtracting consumed ranges. It includes a concrete output example ('app.py 35m, auth.py 20m, total 55m') and explicitly notes that raw heartbeat data is not exposed, differentiating it from sibling tools like wakatime_heartbeats.

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?

Usage is implied rather than explicit. The description indicates it is for obtaining per-file coding time after subtracting consumed ranges, but it does not name alternative tools or state when not to use it. It leaves the agent to infer this from the context of sibling tools such as wakatime_durations and wakatime_mark_consumed.

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