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. What the description adds is genuinely behavioral: it states the per-entry fields (role, is_holding derived from a holding entitlement, is_active tied to this MCP session) and the parent/child semantics with the exact allowed values 'client' and 'subsidiary' versus null. The remaining gap is that no output schema exists, so pagination, ordering, and volume are left unaddressed.

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, the first stating what is returned and the second unpacking the harder fields; the important scoping (only orgs the user belongs to) is front-loaded. The second sentence is dense and chains four field definitions together, which is efficient but slightly harder to scan than a short list would be.

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?

With no output schema and no parameters, the description carries the full burden of explaining the response, and it does so: role, is_holding with its derivation, is_active tied to the MCP session, parent_organization_id, and the meaning of parent_relation. That covers the tricky hierarchy case an agent would otherwise misread. It falls short of 5 only for omitting ordering/pagination and the handoff to switch_organization.

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 no parameter semantics to document and the baseline of 4 applies. The description does not waste space restating an 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?

The first sentence gives a specific verb and resource with an explicit scope: 'List every organisation the authenticated user is a member of.' That is far more precise than a generic 'list organizations' and immediately separates it from write-oriented siblings like create-budget-plan or switch_organization. It stops short of 5 because it never names switch_organization as the tool for changing the active org, which is the main sibling an agent could confuse it with.

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?

Usage is implied rather than stated: the description makes clear this is a read of the user's memberships and that is_active reflects the session's current org, which hints at a discovery-then-switch flow. However, it never says when to call this versus switch_organization, nor any prerequisite such as needing an org id before other org-scoped calls. An agent can infer the flow but must do the work itself.

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