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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered; the description adds real value beyond them by stating 'Nothing is sent to the hardware', which reassures the agent this is a pure inspection step. It also discloses the return payload despite there being no output schema. It doesn't cover failure modes for an invalid or expired code.

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?

Three short sentences: action, precondition, return value and a safety note. Nothing is redundant and the purpose is front-loaded before the setup context.

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?

With no output schema, the description carries the return-value burden and does so ('MIDI output and input ports of their machine'). For a simple two-parameter read-only check, that is nearly complete; only error/expiry behavior for a stale pairing code is left unstated.

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 100%, so both parameters are already documented, including the example code format and the optional user_id. The description only adds provenance context ('the user ... gave you its pairing code'), which is marginal beyond the schema. Baseline 3 is appropriate.

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?

States a specific verb and resource ('Check a relay') and explicitly names what it returns — the MIDI output and input ports of the user's machine. That distinguishes it functionally from relay_send and relay_listen, though it never names those siblings explicitly, so the differentiation is inferred rather than stated.

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?

Gives a concrete usage precondition: the user has opened the relay page or run `osc-bridge connect` and handed over a pairing code. That is a clear trigger condition. It stops short of exclusions or pointing to alternatives such as relay_detect when the precondition is not met.

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