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

Annotations already establish read-only/idempotent/non-destructive, so the description correctly doesn't restate safety. It adds useful behavioral context instead: missing banks fall back to settings and are surfaced in `assumed`, and omitting start_pressure silently assumes an empty tank. It also warns to keep gas litres and bank pressure drop conceptually separate.

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 the purpose, but the body is repetitive ("each bank's pressure afterwards" reappears as "each bank's pressure before and after") and mixes a stack of quoted intents in two languages with the answer-shape narrative. Several sentences could be merged without losing meaning.

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 21 params, nested bank objects, and no output schema, the description does the heavy lifting by enumerating the return contents (O2/He/other gas used, before/after bank pressure, whether the fill works, decant vs booster) and flagging the settings-derived `assumed` values. An agent has enough to call and interpret it, though the decant/booster branch logic remains only sketched.

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%, so the schema already carries all 21 parameters, their enums and defaults; baseline 3 applies. The description adds only the settings-fallback note for banks, which is already echoed in the schema's own `banks` description, so little net new parameter meaning is contributed.

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+resource: litrage of each gas drawn from banks, post-fill bank pressures, and whether banks can still decant. It also anchors itself against a sibling ("Same inputs as blend, plus the banks"), which helps an agent disambiguate. Not quite a 5 because the opening sentence is a dense run-on rather than a crisp one-line purpose.

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?

Provides concrete triggering questions ("how much helium will this fill use", "is my O2 bank enough") and an explicit follow-up route to fills_from_bank. It implies a split from blend via "same inputs as blend, plus the banks" but never states when to pick blend instead, so there is no explicit exclusion rule.

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