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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false). The description adds value beyond that by disclosing the required authorization scope ('Requires service_areas:write scope') and flagging that the association is 'optional scoping', context an agent cannot get from the annotations alone.

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?

Three tight clauses, front-loaded with the core action followed by the auth requirement and the ID-resolution hint. No filler and every sentence carries distinct information.

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 linking tool with no output schema and full annotation coverage, the description supplies the action, required scope, and ID sourcing, which is essentially everything needed to call it. It does not address behavior on an already-existing link, a minor gap against the idempotentHint=false signal.

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 the baseline would be 3, but the description goes further by mapping each required parameter to its source listing tool (list_service_areas → service_area_id, list_sites → site_id), telling the agent how to obtain valid UUIDs rather than just that they are required.

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 resource ('Link a site to a service area') that is immediately distinguishable from create_site, create_service_area, and delete_service_area_site. An agent knows exactly what relation it establishes without opening the schema.

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?

Provides an actionable workflow prerequisite ('Resolve IDs first: list_service_areas → service_area_id, list_sites → site_id'), which tells the agent what to do before invoking. It stops short of naming when to prefer this over any alternative link path, but for a linking tool the prerequisite guidance is the practical usage cue.

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