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

Annotations already establish the safe-read profile (readOnly, idempotent, non-destructive, closed-world). The description adds two genuinely useful operational facts: the credit cost (10, Tier 1) and the group/tradition it belongs to, plus the alias identity. It says nothing about output shape or whether phases are computed for a single moment or a span, which matters for a tool with 15 parameters.

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?

Four short lines, purpose front-loaded, metadata bracketed and clearly separable. Nothing is padded, though the alias note is arguably redundant with the tool name prefix 'hels'.

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 not be explained, but with 33% parameter coverage and no description-level compensation, an agent cannot confidently populate the eleven undocumented inputs. The description also fails to clarify whether stations/phases are natal-moment snapshots or time-series results.

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%, leaving roughly ten parameters (city, date, name, time, latitude, longitude, cosmogram, zodiacType, houseSystem, ayanamsaId) undocumented in the schema, and the description supplies zero parameter meaning to compensate. For a 15-parameter tool this is a substantial gap.

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 names the subject matter ('Heliacal phases and stations') but uses no verb and does not say what is actually returned or computed. It is distinguishable from unrelated siblings, but nothing separates it from near-neighbours like astroway_hels_morning_evening_stars or the canonical astroway_hellenistic_schmidt_stations_and_phases beyond the alias note.

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?

There is no when-to-use guidance, no exclusions, and no comparison to alternatives. The only routing information is the parenthetical alias mapping, which tells the agent this duplicates another tool but not which one to prefer or under what circumstances.

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