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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real behavioral context beyond that: results come from FUSSBALL.DE's own location search, the returned codes are five-digit, and 'no match is a valid empty list' pre-empts a false no-result interpretation. Return-field detail is left to the output schema, which is appropriate.

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?

Four short sentences, front-loaded with what is returned and why it matters; the empty-list caveat and the follow-up call are placed where an agent will read them. Slight redundancy between 'Use it to turn a place...' and 'Use fussballde_match_calendar with a returned postal code' keeps it from being maximally tight.

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 one-parameter lookup with an output schema and safety annotations already present, the description covers everything an agent needs: input intent, the five-digit output shape, legal empty results, and the downstream tool to call. Nothing material is missing.

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?

With 100% schema coverage, the schema already documents q as a place name or postcode prefix of 2-40 characters with examples. The description restates that same meaning ('a place such as Dortmund,' 'postcode prefix') without adding format, matching, or ranking rules the schema lacks. Baseline 3 is correct.

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 verb and resource: it returns German postcodes (with city and district) from FUSSBALL.DE's own location search, given a place name or postcode prefix. That is clearly distinct from every sibling, none of which resolve place names to postal codes.

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 exact use case — turning a place such as Dortmund into the five-digit postal_code that fussballde_match_calendar requires — and names the follow-up call with the returned code. The alternative it feeds is explicit, so no inference is needed.

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