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

The annotations already declare this is a non-read-only, non-destructive, non-idempotent write, so safety is covered. The description adds the required write scope (project_systems:write), which is genuine auth context beyond the annotations, but it does not explain the practical consequence of non-idempotency (duplicate links) or what a duplicate attempt returns.

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, front-loaded sentences with no filler: the operation is stated first, the prerequisite scope second. Nothing is wasted or buried.

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 link tool with full schema coverage, safety annotations, and no output schema, the description covers the essentials (action + required auth). It leaves a small gap around duplicate-link behavior and prerequisite existence checks, which keeps it from a 5.

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 description coverage is 100% – both project_id and system_id are typed as UUIDs and documented as required in the schema. The description adds no parameter-level detail (e.g., that project_id must reference an existing project), so the baseline of 3 is appropriate.

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?

"Link a system to a project" gives a specific verb (link) and both resources, and the word "link" usefully signals this is an association/join operation rather than entity creation, distinguishing it from create_project and create_system. It stops short of naming the closest siblings (create_project_system_class/group, get/list/delete_project_system) explicitly, so an agent must infer the boundary.

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 description states what it does but gives no when-to-use guidance: no mention that the project and system must already exist, no alternative tools, and no clarification versus create_project_system_class or create_project_system_group. The only extra sentence is an auth requirement, which is not usage guidance.

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