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

The description discloses non-obvious behavior beyond annotations: fields must be named in `clear` to be emptied, empty strings are insufficient, and rewriting a photo-embedding body is refused because MCP only exposes `![photo]`. These details go well beyond the destructive/idempotent hints.

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?

Four sentences, each earning its place: purpose, field semantics, sibling routing, and the photo-refusal edge case. The most important information is front-loaded.

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?

The description covers the tool's core semantics, its dangerous edge cases, and its alternative. The output schema and annotations handle the remaining formal details, so nothing essential is missing for an agent to invoke it correctly.

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?

The description adds crucial meaning for `content_markdown` and `clear`, including the empty-string caveat and whole-field replacement model. With schema description coverage at only 25%, it compensates for the most important gaps, though it does not explicitly explain every parameter.

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 opens with 'Replace whole fields on a note,' which names a specific action and resource. It also clarifies the update model (omitted fields unchanged) and distinguishes the tool from replace_in_note.

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 gives an explicit routing rule: for anything short of a full rewrite, use replace_in_note, because it cannot mangle untouched text. This directly tells the agent when update_note is the right choice and when a sibling is safer.

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