markers_add

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

Annotations already declare it is a non-read-only, non-idempotent, non-destructive write. The description adds one genuinely new fact — 'Undoable' — which matters given idempotentHint=false, but it does not say what happens on a duplicate position, whether existing markers are displaced, or what is returned.

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 primary action and immediately followed by the variant condition and the reversibility note. No 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?

For a simple four-parameter write tool with full schema coverage and annotations carrying the safety profile, this is largely sufficient. The only real gap is the absence of an output schema combined with no mention of a return value (e.g. a marker id), which an agent may need for later removal or edits.

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 100% so the baseline is 3; the description earns an extra point by explaining the semantic switch that end_beat triggers (region vs. single marker), which the schema alone only labels as 'End of the section region.'

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?

Specific verb+resource ('Add a marker ... to the timeline') with an extra branch: passing end_beat creates a section region instead of a point marker. That distinguishes it clearly from markers_remove, though it never names the sibling explicitly.

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 by 'add a marker to the timeline' and the end_beat branch hints at when a region is appropriate, but there is no explicit when-to-use vs. alternative guidance (e.g. versus automation or arrangement tools) and no stated preconditions.

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