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

Annotations already declare the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description only needs to add operational context. It does contribute the cost tier (10 credits, Tier 1) and the exact endpoint/method, which are genuinely useful for budgeting and routing, but says nothing about result shape beyond the title, latency, or whether the calc is tropical-friendly.

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 description is a single line plus a compact metadata block; the required-input and cost lines are front-loaded and scannable. It borders on being too terse to be useful, but nothing is padding, so it does not cost much.

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 for a 15-parameter tool with 33% schema coverage and a crowded sibling set the description is far too thin: it gives no indication which optional parameters matter for this tradition or how the result differs from neighboring decan/ruler endpoints. An agent could call it, but with little confidence it chose 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 description coverage is only 33% across 15 parameters, so the description carries a compensation burden it does not meet. It re-lists the four required parameters (date, time, latitude, longitude), which the schema already marks required, and adds nothing about the many undescribed optional parameters (zodiacType, houseSystem, cosmogram, ayanamsaId), whose relevance to a decan-ruler calculation is left to guesswork.

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 a specific astrological technique ('Chaldean decan rulers per planet'), which is enough for an agent to know this produces decan-ruler assignments rather than a general chart. It does not, however, distinguish itself from the several decan/ruler-adjacent siblings (astroway_hellenistic_hand_decennials, astroway_helg_zodiacal_decans, the Greenbaum zodiacal_decans) that a selector must choose among, so it stays below a 5.

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 statement, no prerequisite, and no named alternative. The bracketed block lists required inputs and cost but never says in what situation an agent should pick this tool over the dozen other Hellenistic 'Hand' tools or the decan tools from other traditions.

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