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

Annotations already declare this as a non-read-only, non-destructive, non-idempotent write, and the description adds the concrete required scope (vendor_site_assignments:write), which is genuinely useful auth context beyond the structured fields. However, it does not disclose what happens on a duplicate assignment, whether the link is upserted, or any rate limits, leaving meaningful behavior unstated.

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 core action front-loaded and the scope constraint second. Nothing is padded, and both sentences earn their 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 simple two-parameter junction-creation tool with full schema coverage and annotations covering the safety profile, the definition is nearly sufficient. The only notable omission is duplicate/idempotency behavior, which is relevant given idempotentHint=false.

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% with both parameters (vendor_id, site_id) fully documented as required UUIDs, so the schema carries the parameter burden. The description adds no additional meaning such as format hints or cross-references, which yields the baseline 3.

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 description states a specific verb (assign) and the two resources involved (vendor, site), making the operation unambiguous. It is clear what the tool does, though it does not explicitly contrast itself with the obvious sibling set (create_vendor, create_site, delete_vendor_site_assignment) to confirm it creates the link record rather than the entities.

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 guidance, no mention of alternatives (e.g. bulk_create or update_vendor for existing assignments), and no stated preconditions such as whether the vendor and site must already exist. The only prerequisite given is the scope requirement, which is compliance rather than routing guidance.

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