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

Annotations already indicate destructiveHint=true, so the mutation nature is known. The description adds valuable context: the 'patch is merged field-by-field' (how changes apply), 'immediately or in its line draft' (commit mode), and 'requires edit access' (permission requirement). These go beyond the annotation and clarify consequences without contradiction.

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 concise sentences with zero filler. The main action and mode are front-loaded, followed by merge semantics and permission. No redundancy with schema content; every sentence earns its place.

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 complex tool with a very detailed schema, the description covers the high-level behaviors an agent needs to decide when to call it: update action, dual modes, merge semantics, and access requirement. While it does not describe return values, output schema is absent and the schema itself carries the detailed field semantics, so this is sufficient.

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 the schema already documents all parameters thoroughly. The description adds meaning about the patch parameter's merge behavior and the lineKey/commitMode interplay ('immediately or in its line draft'). This enriches understanding of how parameters relate, which the schema alone does not fully convey.

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 ('an endpoint'), and specifies two modes: immediate or line draft. This clearly distinguishes it from create_endpoint (new endpoint) and delete_endpoint (removes endpoint), and from draft-specific tools like discard_draft_endpoint.

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 implies when to use it: to modify an existing endpoint, either immediately or via its line draft. It mentions the merge behavior but does not explicitly exclude alternatives or state when to prefer create vs update. The two modes are clear, but there is no explicit guidance against using this for creation/deletion. Still, the context is clear enough for an agent.

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