marker_add_region

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

No annotations are provided, so the description carries the full burden. It discloses key behavioral traits: returns both marker_index and region_number, explains the difference between them, notes that region_number is REAPER's display id and can be reused after deletion. This is valuable context for subsequent calls. However, it doesn't mention potential side effects or permissions, which is a minor gap.

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 front-loaded with the core action and the most important behavioral note (return values), followed by a structured Args list. It is appropriately sized and every sentence provides useful information, though the return explanation could be slightly tightened.

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 complexity (6 parameters, no schema descriptions, no annotations, no output schema), the description covers everything an agent needs: what the tool does, when to prefer a batch alternative, what it returns, how to use the return values, and full parameter semantics. It is complete for correct invocation.

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 0%, so the description must compensate. It does so excellently by documenting all six parameters in an Args section: start/end in seconds, name as label, and color_r/g/b with range 0-255. This adds crucial meaning beyond the bare schema types and defaults.

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 states a clear verb and resource ('Add region'), distinguishing it from siblings like marker_add or marker_add_batch. However, it doesn't explicitly clarify that it adds a region marker (a stretch marker) versus a simple marker, which could confuse against marker_add. It does differentiate from add_markers_batch.

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?

Explicitly recommends 'Prefer add_markers_batch for multiple,' giving a clear alternative for batch operations. However, it doesn't specify when to use this tool over marker_add (single marker) or markers_apply, leaving some ambiguity for single vs. region marker decisions.

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