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

Goes well beyond the readOnly/idempotent/openWorld annotations: it shows the exact non-mutating SysEx payload, states 'changes nothing on the device', explains matching against a catalogue, and discloses the failure mode ('devices that do not answer are only listed by port name'). That is exactly the behavioral context an agent needs before calling.

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?

Two dense sentences, front-loaded with the core action and followed by the return contract. No wasted phrasing despite covering mechanism, side-effect status, matching logic, and failure behavior.

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?

There is no output schema, so the description carries the return contract — it names driver ids and identity_hex, and explains the non-responding-device case. Combined with annotations covering safety, an agent has everything needed to call 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?

With 100% schema description coverage, the schema already documents code, user_id, and timeout_ms. The description adds downstream semantics (identity_hex/driver ids feed report_result) but little on the input parameters themselves, so the baseline 3 applies.

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 ('Find which devices are connected to the user's machine through a relay') and names the exact mechanism (MIDI Identity Request SysEx) and what is returned. It is clearly distinguishable from relay_send, relay_listen, and relay_status, which do not perform discovery.

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?

Implies use when you need to discover devices behind a relay and explicitly tells the agent what to do with the result ('best driver ids and identity_hex to pass to report_result'). It does not explicitly contrast against siblings like relay_listen or relay_status, so it stops short of full when/when-not guidance.

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