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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds that results are anchored to a viewing date and span three nested period lengths, but says nothing about output shape or whether birth data must be complete for a valid result. Useful but thin beyond 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?

A single front-loaded sentence with a colon-delimited enumeration of the three period layers, zero filler. It could be marginally clearer by naming the viewing-date anchor before the period list, but it 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?

Five parameters with full schema coverage and no output schema, so the description should at least sketch what comes back (period boundaries, star placements, ratings) and how it relates to tuvi_chart_vn. Neither is present, leaving the agent to guess the result shape for a non-trivial astrology computation.

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 all five parameters including target_date's default-today behavior are already documented in the schema. 'Theo mốc ngày xem' only restates target_date in prose and adds no format or constraint detail beyond the schema. 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?

States a specific verb (Tính) and resource (vận hạn Tử Vi) and enumerates the three scopes it covers: Đại vận 10 năm, Lưu niên từng năm, Nguyệt vận từng tháng. An agent can tell this is a multi-layer fortune-period calculator, but nothing distinguishes it from the sibling tuvi_chart_vn, which likely produces the underlying chart.

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: you call it to see fortune across decade/year/month periods, anchored on 'mốc ngày xem'. There is no explicit statement of when to prefer this over tuvi_chart_vn, no prerequisite such as needing a birth chart first, and no exclusions.

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