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

The annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description meaningfully adds the required auth scope ('contract_sites:write'), which the annotations do not carry. However, it says nothing about duplicate-assignment behavior despite idempotentHint=false, which is the key behavioral question for a join-record creation.

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 zero waste; the core action is front-loaded and the constraint follows. Nothing needs trimming.

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, non-destructive create tool with full schema coverage and no output schema, the description is nearly complete. It could state what happens when the assignment already exists (idempotency is false), but otherwise an agent has what it needs to call it correctly.

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 documented as UUIDs (site_id, contract_id), so the schema does the heavy lifting. The description adds no syntax, format, or relationship detail beyond what the schema provides, making the baseline 3 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?

The description states a clear verb+resource ('Assign a contract to a site'), which precisely identifies this as the join-creation tool. It distinguishes itself implicitly from create_contract (the contract entity itself) and create_contract_document, though it does not name a sibling explicitly.

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 the related delete_contract_site or list_contract_sites siblings, and no note on prerequisites beyond the scope line. Usage must be inferred entirely from the tool name.

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