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

Annotations already declare readOnlyHint, openWorldHint=false, and idempotentHint=true. The description adds that the tool returns a routing list of sibling sites and their MCP endpoints, which is consistent with those annotations and provides useful behavioral context beyond the structured metadata.

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?

A single sentence with no filler: the primary action, object, and purpose are all front-loaded. Every phrase contributes necessary information, making the description compact and scannable.

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-only listing tool, the description fully specifies the output scope (sibling sites, other conditions, MCP endpoints) and the intended use case. An agent has everything needed to decide whether to invoke it and what to expect.

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 has zero parameters, so there is no parameter-level meaning to add. The baseline of 4 applies because schema coverage is trivially complete and the description correctly focuses on behavior rather than non-existent inputs.

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 uses a specific verb ('List') and names a precise resource: sibling Comparison Collective comparison sites for other conditions plus their MCP endpoints. It also states the routing purpose, which clearly differentiates it from generic listing tools like list_services.

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 explicitly ties usage to a user need spanning conditions, giving a clear trigger for when to use this tool. It does not name sibling alternatives or provide explicit exclusions, but the context is clear enough for selection.

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