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

With no annotations, the description discloses useful behavioral details: it auto-resolves wikilinks, leaves unresolved [[...]] literals and returns them, supports [[#<thoughtId>]] disambiguation, and specifies the credit-billing prerequisite. It does not mention idempotency or what happens if the target note does not exist, but the provided behavior is meaningfully beyond the schema.

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 purpose is front-loaded, and the longer guidance is organized under 'Note style' and 'Linking to other thoughts' headings. Each section earns its place by providing necessary formatting rules for a tool that generates note content, though it is slightly verbose.

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?

Given the output schema and 80% schema coverage, the description covers the operation, prerequisite, and content-formatting conventions well. It would benefit from an explicit comparison to create/update siblings and a little more detail on edge-case behavior, but it is essentially complete for an append-to-note tool.

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 80%, so baseline is 3. The description adds substantial value for the markdown parameter by explaining wikilink syntax, external link formatting, bold usage, and unresolved-link handling, and it clarifies npub's role for billing. The dpop_token parameter remains unexplained, but the description goes well beyond schema basics.

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 'Append content to an existing note', which clearly states the verb, resource, and scope. It differentiates from sibling create/update tools through the word 'append', though it does not explicitly name those alternatives.

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 gives a prerequisite ('Requires npub for credit billing') and implies the tool is for appending to a note that already exists. However, it does not explicitly state when to prefer this over brain_create_or_update_note or brain_update_thought, and the style guidance concerns content formatting rather than tool selection.

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