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

The description is genuinely rich about behavior — the 2-minute blocking wait for user acceptance, the clamping to parameter range, gap_ms defaults — but it says plainly that SysEx 'may overwrite the device's memory,' which sits uneasily against destructiveHint=false. An agent trusting the annotations alone would not anticipate that a send can rewrite patch/preset state, so the discrepancy is worth flagging even though the consent gate mitigates it.

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?

One dense paragraph with the primary action front-loaded and the safety warning placed at the end where it applies. A few sentences are long and pack multiple ideas (e.g. the SysEx clause), but nothing is padding.

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 8-parameter, open-world, non-idempotent send tool with no output schema, the description covers the two call modes and the confirmation flow well. It never mentions the sole required parameter, the pairing `code`, nor what the call returns on success or refusal — gaps the schema alone only partially fills.

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 coverage is 100%, so the schema already documents all eight fields; the description still adds real value by showing the shape of device (id or slug) and address ('/filter/cutoff', args [64]), explaining the server transcode into CC/NRPN/note/SysEx, and stating that values are clamped to the parameter's range.

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 — 'Play or set something on the user's hardware through a relay' — and immediately disambiguates the two invocation modes (driver + OSC address vs. raw MIDI hex). It also implicitly separates itself from relay_listen/relay_status, which are the read-side siblings in the same family.

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 concrete conditions: use device+address when you have a driver, use hex for raw bytes, and explicitly routes the agent to list_routes to discover valid addresses. It also warns that SysEx other than Identity Request triggers a user-confirmation prompt. It stops short of stating when to prefer relay_listen or relay_status instead, but the send-vs-receive split is clear from the wording.

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