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

Annotations cover safety (readOnly, idempotent, non-destructive, closed-world), and the description adds substantive behavior beyond them: cost tier, the strict no-fallback language policy, the `missing` list contract, and the partial content coverage (planet-in-sign spans 20 languages; houses and aspects are still being written). That coverage disclosure materially changes how an agent should call and report this tool.

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?

Purpose and the key-grammar essentials are front-loaded, and each sentence carries information. The `missing`/no-fallback rule is arguably restated in the trailing instruction, which costs a little efficiency but reinforces a high-stakes behavior.

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, the description need not document return shape, and it instead covers the non-obvious parts: language fallback policy, the `missing` list, cost, and content coverage per key type. An agent has everything needed to call it and to interpret a partial response correctly.

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 baseline is 3, but the description adds meaning beyond the schema: the 64-key ceiling, concrete key grammar examples, and the fact that language coverage differs by key family (planet-in-sign vs houses/aspects), which affects how the `keys` parameter should be chosen.

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+resource: it returns edited (static) interpretation texts for chart points, explicitly 'no AI at request time', which distinguishes it from the AI/mcp siblings like astroway_mcp_ai_explain_aspect and from the translation siblings. An agent can tell what this tool returns without opening the 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?

Gives clear context for use: it is a static-lookup tool, costs 10 credits, requires keys and lang, and instructs how to handle `missing` results (report unavailable, do not invent or translate). It does not name an explicit alternative tool to use for AI-generated interpretations, so the routing guidance is strong but not complete.

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