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

The annotations already convey that this is a non-read-only, non-idempotent write operation, and the description adds no behavioral context beyond the word 'Register'. It does not disclose duplicate handling, whether an entry is created, or any side effects, though it does not contradict 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?

The description is one short sentence with no filler or repetition. Every word, including 'custom or commercial', adds some information about what can be registered.

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?

The schema covers fields and units, and an output schema exists, so the minimal description is functional for a straightforward creation tool. However, it leaves contextual gaps such as duplicate-name behavior or the relationship between hardness values and mineral concentrations, making it adequate but not complete.

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?

The input schema has 100% coverage, with descriptions for GH, KH, TDS, name, type, notes, calcium, and magnesium. The description contributes no additional parameter meaning, so it stays at the baseline of 3.

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 uses a specific verb ('Register') and a concrete resource ('water formulation'), so the agent can tell it from sibling registration tools like register_coffee or retrieval tools like list_waters. It does not explicitly mention 'recipe' or contrast it with list_waters, but the core purpose is unmistakable.

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?

There is no guidance about when to choose this tool over alternatives, such as using list_waters for retrieval or register_coffee for other entities. 'Custom or commercial' gives a slight scenario hint, but no conditions, prerequisites, or exclusions are stated.

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