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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior beyond them: the month branch is resolved via mid-month jieqi (which determines which month boundary is used) and the cost is 10 credits (Tier 1). It does not contradict the 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?

Two tight sentences front-load the method and scope, followed by compact structured metadata (group, cost). No filler or repetition; every line carries 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 an output schema present, return values need no explanation, and annotations cover safety. However, for an 8-parameter tool with 3 required inputs and 25% schema coverage, the description leaves the date/time/timezone inputs and their interaction underspecified, which is a real gap for correct invocation.

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 only 25% across 8 parameters, so the description carries the burden and fails to compensate. Only 'a specific calendar month' loosely gestures at targetMonth; natalDate, natalTime, targetYear, natalTzOffset, and language are undocumented in both the schema and the description, leaving timezone and year/month coupling unclear.

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 names a specific analytical method (Sheng-Ke + branch-clash) and its scope (a single calendar month), and explicitly frames it as the monthly counterpart to the yearly analysis. It differentiates scope from the sibling astroway_bazi_yearly by implication rather than naming the tool, so it is clear but not maximally sibling-aware.

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?

Framing it as 'same as yearly but applied to a specific calendar month' implicitly tells the agent when to reach for this rather than the yearly tool, but there is no explicit when-to-use, no exclusions, and no mention of the adjacent astroway_bazi_month_pillar (natal month pillar), which could easily be confused with this forecast tool.

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