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

Goes well past the destructiveHint annotation: it discloses that tags replace the entire list, that content overwrites prior content and regenerates the embedding, that a failed embedding aborts the update leaving the node unchanged, and that session auth is required. This is exactly the mutation-risk context an agent needs.

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 sentences, front-loaded with what can be updated, followed by the two highest-risk semantics and the auth prerequisite. No padding or repetition of the tool name.

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?

Covers atomicity on embedding failure, wholesale tag replacement, reactivation, and session requirement for a destructive mutation with no output schema. The only gap is whether the updated node is returned, which is minor 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 100% and the schema already documents full-list tag replacement, empty-array removal, omit-to-keep, and embedding regeneration. The description largely restates those facts, so it adds little beyond what structured fields already provide; 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 (update) plus the resource (an existing knowledge node) and enumerates the mutable fields (status, content, tags) and the side effect of reactivation. The word 'existing' implicitly separates it from the sibling kg_node_create, but no sibling is named, so differentiation is inferred rather than stated.

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?

'Requires an active session' is an explicit prerequisite, and the tag/content sentences describe when each field's side effects apply (full-list replacement, overwrite). It never names an alternative tool or a when-not-to-use case, so usage is clear but incomplete on routing.

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