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

No annotations are provided, so the description carries the full burden. It does well: discloses the exact deterministic algorithm, symmetry, clamping/rounding, band thresholds, and the returned fields. It does not state failure behavior for unrecognized sign strings or confirm there are no side effects / external lookups, which matters for free-text inputs with no enums.

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-loaded with the action and zero wasted sentences — every clause (rule, bands, return fields, URLs, input example) earns its place. The single densely packed paragraph makes the band and return-value details harder to scan than a short structured list would, which keeps it below a 5.

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 no output schema and no annotations, the description must carry everything, and it nearly does: return fields, band meanings, verdict, and method/page URLs are all enumerated. The notable gap is error/edge-case handling for invalid sign names, which the schema cannot express since there are no enums.

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 100% so the baseline is 3, but the description adds real value: 'symmetric' tells the agent sign_a/sign_b order is irrelevant, and the example input plus 'case-insensitive; Hindi sign names accepted' clarifies accepted value space beyond the schema's min/max length constraints.

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?

Opens with a specific verb and resource: 'Score two signs 0-100 with the published rule'. That is unambiguously a compatibility scorer, distinct from the sibling get_zodiac_sign lookup, so an agent can select between them without opening 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?

The description gives strong usage context (accepted input forms, an example input, the published formula, and a method_url) but never explicitly states when to invoke this versus the sibling tool or what happens if the caller only has one sign. Clear context, no exclusions — a 4.

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