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

Annotations already declare the mutating, non-idempotent, open-world profile, so the bar is lower. The description adds genuinely non-structured context: the credit cost, its tier, and its share (~50%) of a free monthly budget, plus an explicit confirm-before-calling instruction. It does not mention auth or rate limits, but the premium-cost disclosure is the salient behavior for this tool.

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?

Front-loads the single high-value sentence describing output, then uses compact bracketed tags for group, endpoint, required params, and cost. Line-efficient overall, though the [Required: chart1, chart2] tag duplicates what the schema already enforces.

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?

With an output schema present the description is not obliged to describe return values, and it covers the artifact contents, cost, and required inputs. One gap: the title advertises 'PDF or HTML' but the description only mentions PDF and no format parameter exists, so output format selection is unexplained.

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 coverage is 67% and the nested chart schema is exhaustively documented (formats, rejected short forms, tz handling, house-system letters). The description only restates that chart1 and chart2 are required and says nothing about fields, language, precision, or whitelabel. Baseline 3 is appropriate when the schema carries the semantics.

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 ('Render') and resource ('relationship synastry PDF') and then inventories the exact contents — side-by-side Big Three, top-40 cross-chart aspect table, per-chart plus combined element/modality balance. That content spec separates it from the data-style siblings (astroway_relational_synastry*) and the narrative sibling (astroway_reports_ai_synastry_narrative).

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?

Gives one real invocation rule — 5,000 credits / Tier 7, confirm with the user first — which is a valuable cost gate. However it never says when to prefer this over astroway_reports_love, astroway_reports_generate, or the AI synastry narrative, so alternative selection is left to inference.

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