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

Annotations already declare readOnly, idempotent, non-destructive and closed-world; the description adds genuinely new context: that answers include amounts, guideline links with dates, application steps and the earliest permitted start of work, that municipality pages and their Markdown versions are linked when available, and an explicit 'without guarantee' caveat. This exceeds what the structured fields convey.

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 core capability and geographic scope are front-loaded in the opening clause, and every subsequent clause carries information. The parenthetical geographic gloss and the trailing 'Without guarantee' are slightly noisy but still earn their place.

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?

There is no output schema, and the description compensates by spelling out the return contents (amounts, guideline link and date, application process, start-of-work timing, municipality page links). Given three parameters with a nested plan object, this is nearly complete; only partial-plan behavior and failure modes for out-of-area postcodes are unaddressed.

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 67% and the eight nested 'plan' fields already carry individual descriptions, so the baseline applies. The description adds only the behavioral consequence of 'plan' (it triggers a grant estimate) and the acceptance scope of 'postcode' (anywhere in Oberbayern), without clarifying cost fields, units, or how partial plans are handled.

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 names a specific resource (municipal grants for rooftop solar, home batteries and plug-in solar) and a specific geographic scope (postcode anywhere in Oberbayern, all 500 municipalities). It also enumerates what the answer contains, and the subject matter is immediately distinguishable from siblings such as battery_savings or eeg_feed_in.

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?

It states the input contract clearly: any postcode in Oberbayern is valid, and supplying a 'plan' switches the tool into grant estimation. However, it never names an alternative (e.g. check_service_area for out-of-area postcodes) or states when not to use it, so the agent must infer routing.

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