playback_timeline

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

Annotations are absent, so the description carries the full behavioral burden. It explicitly discloses read-only status, uses the 🟢/🟡 traffic light, and quantifies API cost ('1 read; +1 if include_queue'). It stops short of describing behavior when no track is playing, but the safety and cost disclosure is meaningful and goes beyond what any structured field provides.

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 compact sentences front-load the core purpose ('Progress forecast — elapsed/remaining...') before the cost/safety suffix. Every clause earns its place — purpose, optional scope, ETA, safety level, and cost — with zero filler.

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?

This is a simple tool with 2 fully documented optional parameters and no output schema. The description covers the return content (elapsed/remaining, queue runway, ETA wall-clock) and the response_format parameter explains output shape. Only an edge-case note (e.g., behavior when nothing is playing) is missing, which is minor for a read-only forecast.

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 100%; both parameters are fully documented in the schema (include_queue's extra GET call and response_format's three output modes). The description adds only a light conceptual link between 'optional queue runway' and include_queue, so the schema carries the heavy lifting and baseline 3 applies.

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?

States a specific verb and resource: 'Progress forecast' with elapsed/remaining for the current track, optional queue runway, and wall-clock ETA. This clearly distinguishes it from nearby siblings like get_now_playing (raw current state), get_queue/describe_queue (queue content), and get_playback_snapshot (state snapshot) by emphasizing prediction/forecast rather than raw retrieval.

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 use case is implied through 'progress forecast' and 'ETA wall-clock', and the cost annotation hints at when include_queue matters, but the description never explicitly states when to choose this over siblings such as get_playback_context, get_playback_snapshot, or describe_queue. No exclusion conditions or alternative routing are provided.

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