create_river_water_body

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

With annotations already covering the safety profile (non-readOnly, non-destructive, non-idempotent), the description adds useful behavioral context: it lists the returned fields, flags max_wave_height and max_wave_height_on_spawn as RE-READ, and notes the body is re-inspected after spawn. It does not mention permission requirements or cleanup, and the schema's reference to a `success` field that is absent from the Returns block is a minor inconsistency.

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 spawn action, and the long Returns block is justified because no output schema exists. The parenthetical 'a river is born at 0.000 -- that is the control case for the lake defect' is cryptic and costs a little clarity, but overall the structure is efficient.

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 spawn tool with no output schema, the description supplies the return shape (actor label/name, body type, zone linkage, wave-height fields, and echoed request), which is exactly what an agent needs. Coverage is strong; the only gap is the absent `success` field and lack of explicit sibling disambiguation.

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 100%, so the schema already documents all five parameters in detail. The description only restates the optional WaterZone link and the wave-height read-back, adding no syntax or behavior beyond the schema; baseline 3 is correct when the schema carries the load.

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: 'Spawn a River AWaterBody actor, optionally link to a WaterZone, and read back its wave height.' This is clear and distinguishable from lake/ocean counterparts by naming the river body type, though it never explicitly routes the agent against sibling tools like create_lake_water_body or create_ocean_water_body.

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 implies usage through the 'river' body type and the control-case framing, and notes that disable_waves is 'normally a no-op here.' However it gives no explicit when-to-use / when-not-to-use guidance or named alternatives (lake, ocean, or add_water_body_to_zone), leaving selection to inference.

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