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

Annotations already declare readOnly/non-destructive, and the description adds cost and side-effect context that annotations cannot express: zero-auth, zero-charge, no paid provider or model call, and no money movement. This is exactly the extra behavioral context the annotations leave out.

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?

Dense and front-loaded with the most decision-relevant fact ('DEFAULT FIRST TOOL'). The return-value enumeration is somewhat listy and partially redundant given an output schema exists, but every sentence carries usable signal.

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 9-parameter tool with an output schema, the description covers when to call, safety/cost profile, and the shape of the result. The only gap is that the optional parameters are left entirely to 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 only 56%, and the description contributes little beyond 'Only task is required,' which merely restates the schema. It does not explain the optional fields (market, quantity, max_budget, interaction_id) that the schema leaves partly undocumented.

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 (preview) and resource (any NEXUS task), and explicitly positions itself relative to siblings: 'Call this before choosing among protected tools.' An agent can tell what this does and where it sits in the flow without opening the schema.

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?

'DEFAULT FIRST TOOL' plus 'Call this before choosing among protected tools for a new external task' gives an unambiguous default and the triggering condition. It also explains the payoff (next.machine_next) so the agent does not need to re-choose afterward.

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