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

With no annotations, the description carries the burden and does disclose the key behavioral fact: the data is the current sky at UTC now at Greenwich, so the agent knows the time and reference frame are fixed, not caller-supplied. It doesn't mention the ephemeris source or precision, which is the only real gap.

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?

A single sentence with the resource and time basis front-loaded and the use cases trailing. Every phrase adds information; nothing is 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?

An output schema exists, so return values need no explanation, and zero parameters means there is little to specify. The description covers the one thing that matters (the fixed time/place frame), leaving only minor gaps such as data precision.

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?

Zero parameters gives a baseline of 4. The description arguably deserves credit here for clarifying the implicit defaults — the timestamp is 'now' and the location is Greenwich — which is the only semantic ambiguity a no-param call could carry.

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 concrete resource — today's planetary positions — and specifies the exact time/location basis (UTC now at Greenwich), which separates it from compute_natal_chart and get_sign_profile. It doesn't explicitly say how it differs from those siblings, but 'today' vs 'natal' is inferable.

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?

Three concrete use cases are given ('transit analysis, daily overviews, and timing work'), so the agent knows the context in which to reach for it. No explicit exclusions or named alternatives are offered, which keeps it from a 5.

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