mcp-score

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set_live_key_signature

Change the key signature starting at any measure in the live score. Specify the measure number and the key using fifths (positive for sharps, negative for flats).

Instructions

Set the key signature from a measure onward in the live score.

Args: measure: Measure number (1-indexed). fifths: Sharps (positive) or flats (negative): 0 = C major, 2 = D major, -3 = Eb major.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`fifths`	Yes
`measure`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 26, 2026
- addedOutput schema / $defs
```
Added value: +{
+  "CommandResult": {
+    "additionalProperties": true,
+    "type": "object"
+  }
+}
```
- addedOutput schema / properties / result / $ref
```
Added value: +"#/$defs/CommandResult"
```
- removedOutput schema / properties / result / title
```
Removed value: -"Result"
```
- removedOutput schema / properties / result / type
```
Removed value: -"string"
```
First observedv0.1.0May 29, 2026

TDQS

A3.6/5.0

Behavior2/5

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

Annotations are absent, so the description must disclose behavior. It states the action ('Set the key signature from a measure onward') but does not mention side effects (e.g., impacts all subsequent measures), reversibility, error handling for invalid measure numbers, or whether the change is immediately applied. Lacks transparency beyond the basic mutation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Concise and well-structured: a single-sentence purpose followed by a clear Args section. No redundant wording, and the most important information is front-loaded. Every sentence adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple mutation with an output schema, the description covers the core action and parameter semantics. However, it lacks usage context (when to pick this over siblings) and behavioral caveats about side effects or error cases. Acceptable but not comprehensive.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so the description fully compensates. It explains measure is 1-indexed and fifths uses positive for sharps/negative for flats with concrete examples (0=C major, 2=D major, -3=Eb major). This adds significant meaning beyond the bare type definitions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Clear verb 'Set' with specific resource 'key signature' and scope 'from a measure onward in the live score.' It distinguishes itself from siblings like set_live_time_signature and set_live_tempo by naming the exact target. An agent can immediately understand the operation without ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus alternatives. It does not mention that other set_live_* tools exist for tempo, time signature, etc., nor does it state prerequisites or exclusions. The description is self-contained but leaves the selection decision to the agent without hints.

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