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

Annotations already declare this a read-only, non-destructive operation, and the description does not contradiction them. It adds behavioral scope: the tool deliberately returns the full set of 14 bodies and defines exactly what 'meaning' contains (symbol, tagine, category, ruling sign), so an agent can predict response shape and cardinality.

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 first sentence is dense and front-loads the main value. However, the sentence 'Perfect for astrology reference apps, planet meaning widgets, ...' is a largely redundant use-case list that does not help an agent call the tool more precisely. One useful sentence plus a partial-purpose sentence; compact but with minor filler.

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 no-required-parameter, read-only list operation, the description and schema together cover invocation, output scope, language switches, compact mode, and where to go for deeper data. No output schema is needed because the description already marks the fields expected. Nothing important 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?

Schema coverage is 100%, with both parameters thoroughly explained in the schema: lang includes a full list of codes, a default, and a translation-fallback behavior, and compact describes the columnar output shape. The description contributes no parameter-level information, but the schema handles that responsibility, which supports the baseline 3.

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 a precise verb ('Returns') and a specific resource ('all 14 astrological bodies') and enumerates its exact contents (Sun through Pluto, lunar nodes, Chiron, Black Moon Lilith) plus the fields returned. It is clearly distinct from the sibling that fetches a single planet profile, so purpose ambiguity is low.

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?

It states the use cases for the list tool and explicitly names the alternative endpoint for more detailed data: 'Use GET /planet-meanings/{id} for complete profiles with detailed interpretations, keywords, temperature, and dignities'. This gives an agent a clear selection rule between the list and the detail endpoint.

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