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

Annotations already establish the safe profile (readOnlyHint, idempotentHint, destructiveHint=false, closed world), so the bar for extra disclosure is lower. The description goes beyond them by documenting the localization behavior of the output (meaningLocalized in the requested language, with translated: false and English fallback while strings are in progress) and the credit tier/cost, which are genuine behavioral traits not captured by annotations.

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 core value proposition (six numbers, one call, credited discount) and the localization caveat are front-loaded, and the bracketed group/endpoint/required/cost block is easy to scan. 'Numerology: Pythagorean system.' is mildly redundant with the group tag, but overall it is tight and well-ordered.

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-value structure needn't be explained, and the description supplies the remaining decision-relevant facts: the six numbers covered, cost/tier, endpoint, required parameters, and the localization fallback. Nothing an agent needs to select or invoke it correctly is missing.

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 60%, with year, fields and precision already documented in-schema; the description only restates the year default and adds nothing about name/date formats or the compact-mode parameters. It also references strings 'in the requested language' even though no language parameter exists in the schema, which adds ambiguity rather than clarity. Baseline 3 is appropriate here.

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 states a specific resource and scope: 'The six core numbers in one call: Life Path, Expression, Soul Urge, Personality, Birthday and Personal Year', enumerating exactly what is returned. This distinguishes it cleanly from the many single-number Pythagorean siblings (astroway_numerology_pythagorean_life_path, _expression, etc.) without the agent needing to open a schema.

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?

It gives clear selection context by contrasting the batch tool with 'six single calls' at a 20-vs-60 credit cost, which tells the agent when this is the right choice. It stops short of explicitly naming the alternative tools or stating exclusions (e.g., when a single-number call is preferable), so it is clear context rather than full when/when-not guidance.

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