fx_get_pin_mappings

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly states 'Read-only' and 'without modifying anything', eliminating any ambiguity about side effects. It also describes the return structure (pin entries with pin, track_channels, low32_raw, high32_raw) and mentions the REAPER >= 6.0 requirement. It doesn't address error conditions or empty results, but for a read-only inspection tool, the key behavioral traits are covered.

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 structured with a one-sentence purpose, a practical use case, return-format details, and argument specifications. It is longer than strictly minimal but each section adds value: the example is illustrative, and the pin-entry breakdown is necessary since there is no output schema. The primary purpose is front-loaded, and the text is not fluff.

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 there is no output schema, the description adequately explains what the tool returns (pin entries with pin index, track channels, and raw bitmasks). It also provides version requirements and a realistic scenario. It does not specify behavior on invalid indices or when no mappings exist, but for a read-only inspection tool of this scope, the provided details are sufficient for an agent to call it correctly and interpret results.

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 by specifying that track_index is '0-based track index' and fx_index is '0-based FX chain index', clarifying the indexing convention and the meaning of each argument. This adds essential semantic information beyond the bare schema types and titles.

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 a specific verb ('inspection') and a specific resource ('FX plugin's audio input and output pin mappings'). It is distinguishable from sibling fx_* tools like fx_get_params or fx_set_param, which handle parameters rather than routing topology. The read-only aspect is explicit, so an agent can tell exactly what this tool does.

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 provides a concrete, actionable use case: 'verify existing sidechain routing without modifying anything — e.g. confirm that Pro-Q 4's sidechain input pins are receiving channels 3/4 before running automated parameter optimisation.' This clearly indicates when to use the tool. It does not explicitly name alternatives or when-not-to-use cases, but the read-only framing and the example distinguish it from routing setup tools, so this is above baseline.

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