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

Annotations already declare this is a non-read-only, non-destructive, closed-world write, so the safety profile does not need restating. The description adds that setting duration converts the marker into a range, which is real behavioral context, but says nothing about persistence, duplication behavior, ordering, or what happens if time exceeds project length.

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 short sentences, front-loaded with the action and followed by the one non-obvious semantic detail. The parenthetical earns its place as an explainer rather than filler; only the slightly informal "Drop a marker" phrasing costs it a point.

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 five-parameter creation tool with no output schema, the definition covers the essential action and the duration behavior, but leaves time units, color/label semantics, and the interaction with add_beat_markers unaddressed. It is enough to attempt a call but not enough to call it confidently.

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 20% (just projectId documented), so the description carries weight and does clarify the key semantic of duration (it turns a point into a range). However, the units for time and duration, and the roles of color and label, are left entirely undocumented, so half the parameter surface remains uninterpretable.

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 ("Drop a marker on the timeline") and adds a gloss on what a marker means in editing terms ("a beat, a line, a moment to cut on"). It does not distinguish itself from the closely related siblings add_beat_markers, update_marker, or remove_markers, so an agent must infer the boundary.

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 parenthetical supplies implicit use cases (marking a beat, line, or cut point) but there is no explicit when-to-use versus add_beat_markers, no mention of prerequisites, and no note about when to prefer a range (duration) over a point marker. Usage is inferable, not guided.

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