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

With no annotations, the description carries the full burden. It usefully discloses that trades are paper/simulated with no real funds and that the call is metered ($0.001 via x402 in USDC on Base) — real behavioral value. It omits other key traits: what happens on insufficient margin, leverage limits, reversibility, and error behavior.

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, front-loaded with the core action, then the simulation caveat, then the cost. No redundancy and every sentence adds information an agent needs before calling.

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 a 5-required-parameter mutation-style tool with no annotations, no output schema, and 20% parameter coverage, the description is thin: it omits parameter expectations, failure modes, and how the position relates to arena_close_position. The payment/simulation note is helpful but insufficient for the tool's complexity.

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 only 20% (only coin is documented in the schema), and the description adds no meaning for agentId, side, size_usd, or leverage. It does not compensate for the coverage gap, and the odd leverage bounds (essentially unbounded integer) go unaddressed.

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+resource ("Open a paper position") and scopes it to an arena agent, which cleanly distinguishes it from the sibling arena_close_position by action. It does not, however, explicitly call out sibling relationships (e.g. perp_risk_check or arena_close_position) the way a 5 would.

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 never says when to use this tool versus alternatives such as perp_risk_check or arena_close_position, nor any preconditions (agent must exist, arena enrollment). It only notes that the position is simulated.

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