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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive). The description adds useful context beyond them: the calculation is deterministic/reproducible ('воспроизводимый расчёт') and the tool returns a link to a symbolic paid reading, an upsell behavior an agent should anticipate.

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?

Two front-loaded sentences that state the computation then its free/paid framing with no filler. Some of the paid-reading detail could be trimmed but it earns its place as a behavioral warning.

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 read-only calculation tool with no output schema, the description explains what is computed and flags the upsell, which is enough for an agent to call it correctly. Minor gap is the absence of any routing versus the calculate_matrix sibling.

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 100%, so both parameters (date format and locale default) are already documented in the schema. The description only reinforces that the date is a birth date; baseline 3 applies.

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 specific verb+resource (Pythagorean square / psychomatrix calculation) and even states what the computation yields (four additional numbers and repeats in cells 1–9). It is clearly distinguishable from pure meaning/lookup siblings like get_card_meaning, though it does not explicitly contrast with calculate_matrix.

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 implies usage via 'by date of birth' but gives no explicit when-to-use guidance, no prerequisites, and no routing rule against the similar calculate_matrix sibling. The free-vs-paid note describes output behavior, not when to select this tool.

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