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

Annotations cover the safety profile (non-read-only, non-destructive, non-idempotent), and the description adds meaningful context they do not: the required service_areas:write scope. It omits what happens if the link already exists (relevant given idempotentHint=false), so it stops short of full behavioral disclosure.

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 tight sentences with no filler: purpose first, then auth/prerequisite detail. Every clause carries operational value.

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 two-parameter junction-creation tool with full schema coverage, no output schema, and existing annotations covering the safety profile, the description supplies everything an agent needs: what it does, the required scope, and how to obtain valid IDs.

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?

Schema coverage is 100%, so both UUID params are already documented (baseline 3). The description goes further by mapping each parameter to the list tool that produces it (list_service_areas → service_area_id, list_system_classes → system_class_id), adding resolution guidance beyond the 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 and relationship: 'Link a system class to a service area.' This makes clear it is a junction/association creation, distinguishing it from create_service_area and create_system_class in the sibling list, which create the entities themselves rather than the link.

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?

Explicitly states the required scope (service_areas:write) and gives the prerequisite workflow for obtaining IDs (list_service_areas → service_area_id, list_system_classes → system_class_id). It does not state when not to use the tool or how it behaves on duplicate links, but the practical usage path is clear.

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