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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds real value with the prerequisite (requires an active Privacy & Cookie Policy) and the granularity note ('Each entry is one service across every site language'), which is non-obvious. It does not, however, describe the returned fields or how the language aggregation appears in the payload.

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 sentences: purpose first, disambiguation second, prerequisite last. Every sentence carries distinct information and nothing is redundant.

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 read-only list tool with full schema coverage and annotations covering safety, the description covers purpose, sibling routing, prerequisite, and entry granularity. With no output schema, it could say slightly more about the returned shape, but an agent has enough to invoke 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 coverage is 100%, so site_id, page, and size are already documented in the schema (including defaults and max page size). The description adds no extra meaning about pagination or site_id semantics, so the baseline 3 applies.

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 ('List the fully custom services of a site') and immediately defines what a custom service is (user-authored, not in the catalog). It explicitly distinguishes the sibling tool list_site_pcp_services for catalog services, so an agent can separate the two without opening a 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?

Gives an explicit when-to-use rule ('services described in the user's own words because the catalog does not list them') and names the alternative path ('Catalog services added to the site are listed by list_site_pcp_services'). It also states a prerequisite condition (active Privacy & Cookie Policy), leaving little to inference.

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