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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that — the field-naming discrepancy with primitive.average_entry (size vs quantity) and the fact that inverse contracts yield a harmonic mean — but it does not discuss edge cases like mixed sides or how fees affect breakeven. Useful but not rich enough for a 4 against already-strong annotations.

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?

Front-loaded with the outcome, then the sibling comparison, then the trigger phrases and return list. Slightly dense with cross-references (primitive.average_entry appears twice), but every sentence carries actionable information.

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 enumerates the returns (averageEntry, breakeven, per-level summary), which covers the main gap. A 5 would need a note on how fees feed into breakeven, since fee_open_pct/fee_close_pct are exposed but only defined in the schema.

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 baseline would be 3, but the description compensates for a genuine trap: it notes each fill is { price, size } while primitive.average_entry calls the same field quantity, preventing a mis-shaped call. It also restates the return fields that no output schema provides.

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?

The first sentence names a concrete verb and resource set — a DCA entry planner producing weighted average entry price, breakeven, and per-level contributions from multiple fills. It also explicitly contrasts itself with the sibling primitive.average_entry, so an agent can distinguish the two without opening schemas.

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?

It states the triggering user intents directly ("what's my average entry?" / "where is my DCA breakeven?") and explicitly routes the simpler bare-average case to primitive.average_entry. Both the use condition and the alternative are named.

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