set_key_signature

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

With no annotations, the description fully carries the burden of transparency. It openly discloses the unsupported status and the technical reason (popover action, tonality cannot be transmitted via Remote Control API). This is exemplary honesty about expected behavior, going beyond what annotations might provide.

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 three sentences, front-loaded with the critical unsupported warning, then explains why and gives a parameter example. Every sentence adds necessary information with no fluff, making it appropriately sized and well-structured.

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 an unsupported tool, the description covers the main requirements: what it attempts, why it won't work, and the parameter format. It does not describe the return value or error behavior, but given the explicit 'not supported' disclosure, the context is sufficient for an agent to decide not to call it.

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?

The schema has only a 'key' parameter with no description (0% coverage). The description compensates by providing concrete examples ('C major', 'G major', 'F minor') and clarifies the expected format. This adds meaning beyond the bare schema, though it does not explain defaults or validation rules.

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 the tool sets a key signature, but immediately qualifies it as 'NOT yet supported over the API.' This makes the purpose clear but not fully actionable. It does not explicitly differentiate from siblings like set_time_signature beyond noting the unsupported status, so it falls short of a 5.

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 explicitly warns that the tool is not supported, implying 'do not use this to set a key signature.' It draws an analogy to time signature being a popover action, giving context for why it fails. However, it does not suggest any alternative tool or workaround, so it lacks a full when-to-use versus alternatives.

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