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

Annotations already establish that this is a non-read-only, non-idempotent, non-destructive mutation. The description adds that the service must already be site-attached and identified by its primary key, but it does not disclose whether omitted optional fields are preserved or cleared, nor any side effects or permissions.

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?

The description is a single front-loaded sentence followed by one targeted usage note. Every word earns its place, and the most important scoping information appears first.

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?

The schema documents parameters and annotations cover the basic safety profile, but the description leaves update semantics ambiguous: it is unclear whether omitted array fields are replaced wholesale or merged. Without an output schema, success/error behavior is also not communicated.

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%, so all four parameters are already documented. The description repeats the primary-key origin already present in the schema for id, adding little semantic value beyond what the schema provides.

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 clearly states the action and resource: 'Update a PCP service added to a site.' This targets a specific existing relation rather than a global service or site-level setting, distinguishing it from siblings like update_site, create_site_pcp_service, and delete_site_pcp_service.

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 gives a clear prerequisite: use the primary key returned by list_site_pcp_services or create_site_pcp_service. This tells the agent where to get the required id, but it does not explicitly contrast with create/delete or state when not to use this tool.

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