Update contact

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds that only existing contacts are touched and that status changes can effect an unsubscribe, but says nothing about permission requirements, whether omitted fields are cleared or preserved, or tag-removal side effects.

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 front-loaded sentence with no filler, and the parenthetical example earns its place. It is efficient, though it is arguably too terse for a seven-parameter mutation tool.

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?

With no output schema and only 43% parameter coverage across seven parameters, the description leaves real gaps: partial-update semantics, add/remove tag asymmetry, and how the required listId and contact pair interact are all unaddressed. The annotations cover safety, which lowers the bar, but the definition is still incomplete for a tool of this complexity.

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 43%, so the description must carry weight; it does map four of the seven parameters (email_address, fields, add_tags/remove_tags, status) and ties the status enum to a real scenario via 'unsubscribe'. It still does not distinguish add_tags from remove_tags, nor mention the required listId/contact pair beyond what the schema already documents.

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 states a specific verb (Update) and resource (contact) and enumerates the mutable surface: email, fields, tags, status. The word 'existing' implicitly separates it from the upsert_contact sibling, but the distinction is never made explicit, so an agent must infer it.

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 parenthetical '(for example, unsubscribe someone)' supplies one concrete use case, and 'existing contact' hints at the boundary with upsert_contact. However, there is no explicit statement of when to prefer this over upsert_contact or delete_contact, nor any prerequisite guidance.

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