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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds real value by disclosing that the response includes a per-service enabled flag, though with no output schema it could say more about the shape of the result (e.g., IDs needed for follow-up calls).

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?

One tight sentence plus the endpoint reference. Nothing is wasted, and the key detail (services and their enabled state) is front-loaded.

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 zero-parameter read tool with annotations and no output schema, the description covers what the tool returns at a high level. It stops short of noting the identifiers an agent would need to chain into shipday_check_on_demand_availability or shipday_get_on_demand_estimate.

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?

The tool takes zero parameters, so the baseline of 4 applies. The description correctly signals that no filtering arguments are needed, since scope is the whole account.

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 ('List') and a specific resource ('third-party on-demand delivery services') with concrete examples (DoorDash, Uber) and the account scope. It is clearly distinguishable from siblings like shipday_list_carriers and shipday_get_on_demand_details.

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 phrase 'available to the account and whether each is enabled' implies the discovery use case, but it never says when to pick this over shipday_check_on_demand_availability or shipday_get_on_demand_details, nor does it state prerequisites. Usage is inferable but not explicit.

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