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aj-dev-smith

duck-mcp

by aj-dev-smith

Drive the duck

duck_drive
Idempotent

Command the simulated robot's walking velocity (forward, left, yaw) and optionally run it for a set duration, then stop and return the resulting state.

Instructions

Set the walking velocity intent. vx: forward m/s (max ±0.3; the policy tracks ~half the commanded speed, so command 0.25+ for a brisk walk), vy: leftward m/s (max ±0.2), wz: counterclockwise yaw rate rad/s (max ±1.5). Nonzero engages the walking policy; all-zero hands back to standing.

With duration_s (max 10): drive for that long, then stop and return the resulting state — one call instead of drive/poll/stop. Without it the intent persists until changed: the robot keeps walking between your tool calls, and the sim runs in real time, so returned state is already slightly stale when you read it.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
vxYes
vyNo
wzNo
duration_sNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
okYes
rpy_degYesTrunk orientation [roll, pitch, yaw], degrees
sittingYes
uprightYesFalse once tilted past ~45 deg. There is no self-recovery policy: if the duck falls, use duck_reset.
vel_cmdYesCurrent sticky velocity intent [vx, vy, wz]
behaviorYesEpisodic trick currently running, else null
position_mYesTrunk world position [x, y, z], meters
sim_time_sYesSim clock, seconds. The sim runs in real time; this snapshot is stale on arrival.
ground_pickYes
vel_body_mpsYes
yaw_rate_rpsYesYaw rate, rad/s, counterclockwise positive
active_policyYesWhich ONNX policy is driving: standing, walking, sit, ground_pick, kick_left/right, roulade
ball_position_mNoBall world position [x, y, z], meters (ball scene only)
trunk_height_mmYesTrunk height above floor, mm (~116 standing)
Behavior5/5

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

Adds substantial behavioral context beyond annotations: intents persist across calls, the sim runs in real time, returned state is already slightly stale, nonzero values engage walking, and all-zero returns to standing. It also discloses policy tracking behavior and commanded-speed scaling. No contradiction with annotations.

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?

Two dense paragraphs with no filler. The opening sentence states the core purpose, parameter details are grouped logically, and the duration_s alternative is explained in a dedicated paragraph. Every sentence adds operational value.

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

Completeness5/5

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

For a 4-parameter tool with no schema descriptions, the description covers all parameters, limits, behavioral persistence, and the optional duration mode. The output schema exists, so return values do not need to be described. Nothing essential is missing for an agent to invoke this tool correctly.

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 carries the full burden for parameter meaning. It explains vx, vy, wz with units, sign conventions, and max magnitudes, plus duration_s semantics and the all-zero special case. Every parameter is given actionable meaning beyond the bare schema.

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?

States a specific verb and resource: 'Set the walking velocity intent.' The description clearly distinguishes this from siblings by explaining when velocity intents engage the walking policy and when they hand back to standing, and it contrasts the one-call duration mode with drive/poll/stop.

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

Usage Guidelines5/5

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

Explicitly describes the two usage modes: with duration_s for a self-terminating drive, and without it for persistent intent. It also tells the agent when to use the shorter one-call form instead of drive/poll/stop, which routes to the relevant alternative behavior.

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

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