explore_human_design_transit

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

Beyond the annotations (readOnlyHint=true, destructiveHint=false), the description discloses significant behavioral details: a 3-credit cost per call, premium tier status, return format differences between MCP Apps-capable hosts (interactive overlay) and fallback (text summary), use of NASA JPL DE440 ephemerides, and that the call is rejected if neither location nor lat/lon is supplied. These specifics go beyond the basic safety hints.

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 generally well-structured: a clear two-sentence core purpose, followed by bullet-like details on credits, output, tier, ephemeris source, and a disclaimer. The disclaimer about Ra Uru Hu and OpenEphemeris independence is not relevant to tool invocation and could be considered noise, but it does not significantly bloat the description.

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?

Despite lacking an output schema, the description tells the agent what to expect: an interactive overlay in MCP Apps-capable hosts or a text summary elsewhere. It also provides credit cost, location requirements, and ephemeris quality. Some edge behaviors (e.g., exact error handling for ambiguous locations) are only hinted at in the schema's location parameter, but overall it is fairly complete for a read-only tool.

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?

The input schema already provides 100% description coverage for all 8 parameters, so the baseline is 3. The description does add one extra semantic constraint—the call is rejected without location/lat-lon information—which is not reflected in the schema's required fields. However, it does not add per-parameter syntax or format details beyond what the schema already documents, so it stays at baseline.

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 clearly states the tool's function with a specific verb ('Overlay') and resource ('planetary transit on a person's natal Human Design bodygraph'). It distinguishes itself from siblings like 'explore_human_design' (natal chart only) and 'ephemeris_transits' (raw transit data) by emphasizing the overlay and highlighting of completed channels/defined centers, which is the core of a transit reading.

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?

The context is implied: it is for Human Design transit readings. However, there is no explicit guidance on when to choose this tool over alternatives such as 'ephemeris_transits' or 'explore_transit_timeline'. It doesn't mention when not to use it or name any alternative tools, so the agent must infer its applicability.

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