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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral facts absent from the annotations: the POST endpoint and the 50-credit Tier 3 cost, which an agent needs for budget decisions. It stops there, offering no note on compute weight or result size, though the presence of an output schema lowers the need for return-shape detail.

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 output is short, front-loaded with the core sentence, and the bracketed metadata block is scannable rather than wasteful. Nothing is padded, though the bracketed lines repeat information (required parameters) that the schema already provides.

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?

For a 15-parameter endpoint with one-third schema coverage, a single sentence plus four bracketed metadata lines leaves substantial gaps: which planet, how the geography is returned, and how it relates to the sibling geo tools. The existence of an output schema excuses it from describing return values, but not from the input and selection gaps.

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 real burden here and does not meet it. It contributes nothing about date/time format, latitude/longitude semantics, ayanamsa, house system, or the compact-mode fields/precision controls. Worse, it references 'a given planet' as an input while no planet parameter exists in the schema, which can send an agent looking for a field that isn't there.

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 and resource: 'Find all geographic locations where a given planet is exactly at the zenith (MC) at the birth moment.' That is far more informative than the bare title 'Zenith' and lets an agent place it in the geo/astrocartography family. It does not, however, distinguish itself from the many similar siblings (astroway_geo_acg, astroway_geo_local_space, astroway_geo_parans), so an agent still has to guess which geo variant to pick.

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 prerequisites, and no named alternative among the numerous geo siblings. The phrase 'at the birth moment' weakly implies a natal-chart context, but nothing tells the agent when zenith lines are preferable to ACG, local space, or paran output.

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