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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds non-obvious behavior: results are permission-scoped to the caller's access and include agency membership and write-access state, which the agent cannot infer from the annotations.

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 sentences, zero filler, scope stated first and the disambiguation rule second. Every sentence earns its 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?

For a no-parameter read-only list tool with an output schema and annotations, this is nearly complete. Minor gaps: no mention of pagination or result ordering, and the German text sits in an otherwise English tool surface, which is a mild consistency risk for downstream agents.

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?

Zero parameters, so the baseline is 4. The description still contributes by documenting the 'Agency/slug' identifier format that the returned workspace values must use downstream.

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?

Specific verb+resource with clear scope: all workspaces the caller's access can reach, enumerating the included attributes (agency, write access, configured data sources). It does not explicitly distinguish itself from the sibling gtm_list_workspaces, so an agent could still hesitate between the two 'list workspaces' tools.

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 second sentence gives a real usage rule, but it is about how to pass the returned value to other tools ('Agentur/slug' when slugs collide across agencies), not about when to call this tool versus alternatives. No explicit when/when-not guidance.

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