fl_set_playing

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

Annotations already indicate a destructive write (destructiveHint true, readOnlyHint false). The description adds unique behavioral context: that the change is verified on a later FL idle tick, implying asynchronous verification. This goes beyond what annotations convey, adding timing and verification semantics without contradicting the annotation safety profile.

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 a single, tightly written sentence that conveys the core action, the absolute (non-toggle) nature, and the verification step. There is no fluff or repeated information from the schema or annotations.

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?

Given the presence of an output schema, full parameter descriptions in the schema, and annotations for safety/destructiveness, the description covers the essential purpose and timing. It does not elaborate on failure handling or the expected_before parameter, but those are documented in the schema. The description is sufficient for an agent to correctly invoke the tool in most scenarios.

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 has 100% description coverage, so all three parameters (playing, expected_before, session_fingerprint) are already explained. The description does not add additional parameter-level details beyond what the schema provides, so the baseline score of 3 is appropriate.

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 purpose: to set playback to an absolute state (not a toggle) and verify it later. This specific verb-resource pair distinguishes it from siblings like fl_stop (stop) and fl_set_song_position (position), and the 'absolute state' phrase clarifies it is for play/pause rather than a toggle.

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 does not explicitly name alternatives or state when to use this tool vs. others (e.g., fl_get_transport_state for reading). The phrase 'absolute state' implies it is for setting play/pause rather than toggling, but there is no direct guidance on when to prefer it over other playback-related tools. Usage is implied but not stated explicitly.

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