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

With no annotations, the description carries the behavioral burden, and it does disclose that the tool is free and callable without an API key — genuinely useful auth/cost context. It says nothing about return shape, pagination, or rate limits, though the presence of an output schema covers return structure.

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?

Two short fragments with no padding, and the cost/access constraint is stated immediately. Very terse, but every clause carries 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 zero-parameter, output-schema-backed listing tool, the description covers what the tool returns and the key caller-facing constraints (free, no key). Nothing critical for invocation is missing.

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?

The schema has zero parameters, so there is nothing to document; the baseline of 4 applies. The description correctly implies a no-argument listing call.

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 description states it returns per-tool pricing and descriptions, a clear resource scope. Since all siblings (compatibility, day_pillar, monthly, saju_chart, unse) are divination tools, this one is distinguishable as a metadata/pricing lookup, though it is phrased as a noun list rather than a verb+resource action.

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?

Usage is only implied: an agent can infer it should call this to learn about pricing or tool descriptions before using the paid siblings. There is no explicit when-to-use/when-not statement or reference to alternatives.

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