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

Annotations already declare this a safe, idempotent, non-destructive read, so the safety profile is covered. The description adds genuine behavioral context beyond that: the BPHS A.39 cancellation rule that makes a double-Manglik pairing come out as 'cancelled' rather than 'incompatible', which an agent could not infer 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?

Two sentences, zero filler, with the purpose and the decisive rule front-loaded before the verdict enumeration. Nothing repeats the name or title.

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 return format needn't be spelled out, and annotations cover the safety profile. The description supplies the purpose and the interpretive rule; it could be slightly richer on prerequisites (e.g. that two full birth charts with time and coordinates are required), but nothing essential 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 100% and the nested chart objects document every field, so the baseline is 3. The description adds nothing about chart1/chart2, fields, or precision beyond what the schema already provides.

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 (compares) and resource (Manglik status of both partners), plus the exact rule applied (BPHS A.39 mutual cancellation) and the possible verdicts. The phrase 'both partners' distinguishes it from the single-chart sibling astroway_vedic_compatibility_manglik_check without opening either 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 context (two-person Manglik compatibility) is implied by 'both partners' and 'verdict {compatible|cancelled|incompatible}', but there is no explicit when-to-use statement, no when-not, and no routing among the many compatibility siblings (ashtakoot, dashakoota, full, manglik_check). Usage is inferable but not stated.

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