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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered by structured data. The description adds only ''Returns: {total_kg}'', a return detail that is also redundant with the existing output schema, and says nothing about units, precision, or edge cases; it neither contradicts nor meaningfully extends the 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?

Two short sentences, with the core purpose front-loaded ahead of the cross-reference pointer. Nothing is padded, though the ''Returns: {total_kg}'' clause is largely redundant given the output schema.

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 simple, three-parameter read-only calculator with full schema coverage, rich annotations, and an output schema, the description supplies enough to call the tool correctly. The remaining gap is only that the large gardening-sibling cluster is not disambiguated.

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% with two enum-constrained parameters, so the schema already documents each field. The description names crop type and soil type but adds no semantics beyond them and never mentions surface_m2, so it does not exceed the schema baseline.

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 NPK fertilizer quantities'') plus the two driving inputs (crop type, soil type), so an agent immediately knows what the tool produces. It does not, however, differentiate itself from adjacent gardening siblings such as calculate_garden_soil, calculate_lawn_seed, or calculate_raised_bed_soil, so sibling selection still requires inference.

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 phrasing ''based on crop type and soil type'' implies the scenario where this applies, and the ''See list_bundles'' pointer offers a discovery path. There is no explicit when-not guidance or named alternative for adjacent cases (e.g. soil amendment vs. seeding vs. fertilizing), leaving usage only implied.

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