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

Annotations only declare the generic mutation profile (readOnly=false, destructive=false, idempotent=false), and the description adds substantial context beyond that: project scoping, that the result echoes project identity, that most kinds never move sound/length while ramp re-anchors every later item, and that reverse/remap/stutter/ramp refuse spoken words without allow_speech. Error behavior and reversibility are not covered, keeping it from a 5.

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?

It is a single dense paragraph, but it is front-loaded with the most important constraint (PROJECT-SCOPED) and every clause carries concrete information rather than filler. Readability suffers slightly from the run-on structure.

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 12-parameter tool with a nested echo object, two enums, and no output schema, the description covers the critical operational facts: scoping, kind semantics, sound-handling differences, and speech-refusal rules. It omits the timing parameters and exact return shape, but it is largely sufficient to call the tool correctly.

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 coverage is only 33%, so the description must compensate. It usefully documents kind semantics, factor range (0.25-0.9), posterize frames 2-8, stutter frames x repeats, remap curve values, and allow_speech, but leaves start, end, id, and word entirely unexplained. Partial compensation lands at the baseline.

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 names a concrete verb+resource (add time effect) and enumerates the seven kinds (reverse, echo, posterize, stutter, interpolate, remap, ramp) with a gloss of each, so the agent understands the tool's domain well. It does not explicitly differentiate itself from siblings like set_speed_ramp or add_freeze_frame, which limits it to a 4.

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?

It implies when each kind applies (e.g., 'ramp is a real speed change' vs 'picture-only devices') and states the allow_speech condition, but it never says when to pick this tool over alternatives such as set_speed or set_speed_ramp. Usage is inferable rather than stated.

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