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

Annotations already flag destructiveHint=true and idempotentHint=false, and the description earns credit on top by explaining *what* is destroyed (stored updates listed in replaces are deleted after the write) and the merge-not-overwrite semantics. It also discloses the edit-access and Pro-plan requirements. Missing only failure/conflict behavior when a merge is rejected.

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 core action is front-loaded, but it is delivered as one dense run-on sentence, and the clause 'listing in replaces the stored updates it contains' is grammatically tangled enough to slow comprehension. No filler, but readability costs it a point.

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, an agent can still act correctly: annotations cover the safety profile and the description covers auth, tier, merge semantics, and the compaction path. The only gap is that it never says what a successful write returns or how a ref for later replaces is obtained.

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 the baseline is 3; the description adds value by clarifying that ciphertext is produced client-side in the read_note_ciphertext format and that replaces is an owner-only compaction mechanism. It doesn't add detail on the id format or size limits, but those are already well covered in the schema.

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: adds one encrypted Yjs update to an end-to-end encrypted note. It also pins the payload format by referencing the sibling read_note_ciphertext, which separates it from the plaintext update_note and from create_note_ciphertext. It never explicitly contrasts itself with those siblings, so it falls short of a 5.

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 real usage context: the update merges live with concurrent editors, and the compaction path (send the whole note as one update plus replaces) is spelled out for owners. Prerequisites are named ('Needs edit access. Pro.'). It stops short of saying when to use this versus update_note or create_note_ciphertext.

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