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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses result uncertainty, the degraded-output mode for unknown birth times, and a privacy guarantee covering request bodies, queries, access logs, stats and errors. This is operational context an agent cannot get from the schema.

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 purpose, then usage, then edge cases and privacy. The multilingual keyword list is a little listy but earns its place for matching user phrasing; otherwise the sentences are dense and purposeful.

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 values need not be explained, and the description notes uncertainty, one-line meanings and links anyway. The main shortfall is undocumented geographic/time parameters against a 9% coverage schema, which an agent must infer.

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 9% with 11 parameters, so the description must carry the load. It covers lang fallback, time_precision='unknown' behavior and missing birth_time, but says nothing about latitude/longitude vs place_id, timezone, ambiguity, approx_window_minutes, or utc_offset_override_sec. Partial compensation, significant remaining gaps.

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 ('Calculate Sun sign, Moon sign and rising sign together') and immediately routes the user's phrasing to it. Clear distinction from siblings like get_sun_sign and calculate_birth_chart, which cover narrower or broader scopes.

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?

Explicitly names trigger utterances in two languages and, crucially, gives a decision rule for incomplete input: ask for missing birth time/birthplace instead of guessing, and fall back to 'unknown' semantics (no Ascendant/houses, both Moon signs) when time is unavailable. That is when-to-use plus edge-case handling.

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