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

Annotations already cover read-only/idempotent/non-destructive/closed-world, yet the description adds material the annotations cannot convey: the interpretation is symbolic and not a scientific prediction, and no birth data is stored or logged including request bodies, queries, access logs, stats and errors. The language fallback behavior completes the picture.

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?

Front-loaded with the core verb and illustrative examples, then constraints, then the privacy note. Dense and largely waste-free, though the example list and trailing privacy sentence make it a long single block rather than cleanly segmented guidance.

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?

An output schema exists, so return values need no explanation; the description instead covers the items an agent genuinely needs — input id conventions, one-sign-or-one-house constraint, symbolic framing, and data-handling posture. Only the mutual-exclusion behavior when both sign and house are supplied is left unspecified.

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?

With only 25% schema description coverage the description must carry weight, and it does: it specifies that body_or_angle and sign require canonical English ids (so callers must not pass 'Venus' or 'Venere'), and it adds the sign-vs-house exclusivity rule that the schema itself does not express. It does not explain the house/body interaction in the no-sign case beyond a phrase.

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 ('Read the free corpus meaning of a placement') and backs it with six concrete input examples spanning both languages and all three lookup shapes. The role is clearly distinguishable from sibling calculation tools like calculate_birth_chart or get_planet_positions, which return astronomical data rather than interpretation.

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 concrete operating context: 'One sign or one house per call; no sign/house returns the body meaning,' which tells the agent how to shape the call and what the degenerate case does. It does not name alternatives or say when a caller should prefer this over a computation sibling, so it stops short of a 5.

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