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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's contribution is the cost metadata ('10 credits (Tier 1)') and the endpoint, which are genuinely useful and not present in structured fields. It does not disclose response shape, but an output schema exists to carry that.

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?

The purpose sentence is front-loaded and free of filler, and the bracketed metadata block is compact and scannable. The required-parameter line is arguably redundant with the schema, which costs it a point.

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 15-parameter calculation tool with tropical/sidereal and multiple ayanamsa options, the description does not indicate that the frame of reference is selectable or which defaults apply. It is adequate on cost and endpoint and an output schema covers returns, but the omission of frame-related options leaves a meaningful gap.

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 33% across 15 parameters, and the description compensates by re-listing the four required params (date, time, latitude, longitude) that the schema's required array already declares. It adds nothing about the consequential optional parameters (zodiacType, ayanamsa/ayanamsaId, timezone, precision, fields) that materially change the returned longitudes.

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 a specific verb and resource ('Calculate raw planet longitudes') and immediately bounds the scope with '(no houses, no aspects)'. That negative scope cleanly separates it from the heavier sibling astroway_western_chart, so an agent can pick it without opening either 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?

The parenthetical 'without full chart context (no houses, no aspects)' effectively tells the agent when this tool is the right level of detail, i.e. when only longitudes are needed. It stops short of naming an explicit alternative tool (e.g. astroway_western_chart) or stating when-not conditions, so it is clear context without explicit routing.

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