list_categories

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

No annotations are provided, so the description carries the burden, but it does disclose the return shape (a dictionary of main categories and subcategories), which helps an agent plan. It says nothing about read-only nature, authentication, or rate limits, though for a zero-parameter enumeration tool the behavioral risk is low.

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?

Two short sentences with the purpose front-loaded and no filler. The 'Returns:' clause is partly redundant with the existing output schema, which slightly dilutes it but does not hurt readability.

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 zero-parameter listing tool with an output schema, the description is close to sufficient, but it omits any routing guidance against get_category_filters, which is the one thing an agent actually needs to choose correctly among the sibling tools.

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 tool takes zero parameters, so there is nothing parameter-specific to document; the baseline for 0 params is 4. The description cannot add parameter meaning beyond the empty schema.

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 ('List') and resource ('main categories and common subcategories') scoped to Marktplaats, so the agent knows exactly what it returns. However, it never distinguishes itself from the close sibling get_category_filters, which also deals with categories and could easily be confused with this tool.

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 when-to-use or when-not-to-use guidance and no alternative tool is named, even though get_category_filters is an obvious candidate an agent might pick instead. Usage is only inferable from the tool name and the word 'List'.

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