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

Annotations already declare write (readOnlyHint=false), idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations and schema do not carry: the 4000-character cap and, importantly, that an empty string clears the note rather than erroring.

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?

Two tight sentences, front-loaded with the core action and followed by the two operating constraints (size cap, clearing behavior). No filler or redundant restatement of the title.

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 small mutation tool with no output schema and annotations already covering safety and idempotency, the description supplies the non-obvious semantics an agent needs (replace vs. append, empty-string clears, size limit). It omits any mention of the confirm/guard interaction, but that is defined in the schema itself.

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 67%; site_id and confirm are documented in the schema, but the note property only carries type/maxLength. The description compensates by explaining the clearing semantics of an empty note value, which the schema does not express, and repeats the length bound meaningfully.

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+resource ('set/attach or replace your private note on a site') and discloses the replace-not-append semantics. It distinguishes itself from the nearby set_creator_note sibling implicitly by scoping the note to a site rather than a creator, though it never names that sibling explicitly.

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?

It conveys what the operation does but gives no when-to-use guidance, no prerequisites, and does not point at any alternative such as set_creator_note or set_website_contact. The 'empty string clears it' clause is behavioral, not usage routing.

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