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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds substantive behavioral context beyond that: 'The year and month pillars here are attributed by whole days' explains the solar-term boundary rule, and 'the response says exactly what it rules on rather than reducing the day to a single score' sets expectations about output granularity. No contradiction with 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?

Three information-dense sentences with no filler. The core purpose is front-loaded, followed by the most non-obvious behavioral rule (whole-day solar-term attribution), and closed with concrete use cases. Every sentence earns its place.

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 complex almanac tool with no output schema, the description names the key return components and gives a decision-relevant behavioral rule about pillar attribution. Combined with 100% schema coverage, an agent has enough to select and invoke the tool correctly without missing critical context.

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 the schema already documents date format and range, lang enum/fallback, and compact shape. The description's note about whole-day pillar attribution adds interpretive context but not parameter-level semantic details beyond what the schema provides, so the baseline 3 applies.

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 opens with 'Return the full almanac reading of one day' — a specific verb and resource — then enumerates the returned components: lunisolar date, pillars with Na Yin, day officer, lunar mansion, clash animal, and favoured/opposed activities. This clearly differentiates it from sibling tools like the monthly or solar-terms endpoints, and explicitly notes it does not reduce the day to a single score.

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 provides clear context: 'Built for date pickers, daily calendar widgets, and wedding or opening date tools.' It implies this is the per-day almanac tool, but it does not explicitly say when not to use it or name alternatives such as the monthly or solar-terms endpoints, so it misses the full 5.

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