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

With no annotations, the description carries full responsibility for behavior. It transparently discloses that there is no federal purchase premium (only VAT exemption), that programmes vary by state, and that it provides an amortization calculation. It also notes the Stand (08/2026), showing currency. It doesn't describe potential limitations like lack of exact programme details, but it is notably honest about what the tool does and does not include.

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 a single, dense sentence that front-loads the main topic (Balkonkraftwerk-/Speicher-Förderung in Deutschland) and then efficiently lists key covered points (state programmes, ~100€ bonus, apply-before-buying, payback math, no federal premium). While it is long, every clause adds distinct information with no redundancy.

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?

Given the tool has no output schema and 4 optional parameters, the description is solid: it states the topic, key facts, and the central calculation (payback with grant). It doesn't describe exactly what the output format will be, but for an informational tool this is acceptable. The caveat about no federal premium is important and included, making the description contextually adequate.

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 already provides full descriptions for all four parameters (100% coverage). The tool description adds context by linking the parameters to the payback calculation (e.g., preis_eur, zuschuss_eur, ersparnis_eur_jahr) and mentions the ~100€ storage bonus, which helps the agent understand how zuschuss_eur might be used. This goes beyond the schema's basic descriptions.

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 clearly identifies the tool's purpose: explaining German subsidies for balcony solar/storage systems and how a grant shortens payback. It specifies the resource (Balkonkraftwerk-/Speicher-Förderung), scope (Germany, state programmes), and covers payback arithmetic, which distinguishes it from the sibling tools that focus on other home-energy topics.

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 description provides clear context on what the tool covers (state programmes, storage bonus, apply-before-buying rule) and implies when to use it (when researching balcony solar subsidies). It doesn't explicitly state when not to use it or name alternatives, but the context is sufficient given the unique focus.

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