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

"Nothing existing is changed" usefully discloses that this is additive, and "and/or" clarifies that contact_id and project_id may both be supplied. However, it never says what is returned (no output schema exists, so the note ID/response shape is unknown) or whether any permission/scope is needed. Note the mild tension with destructiveHint=true, which the description implicitly softens rather than contradicts outright.

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 short sentences; the operation class ("WRITE:") is front-loaded and the side-effect statement follows immediately. Every clause carries information.

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 6-parameter mutation with no output schema, the description covers intent and side-effect scope but omits the return value, whether a note can exist with no contact/project attachment, and any permission prerequisites. Enough to call it, not enough to predict the result.

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 subject, info, user_id default, contact_id, project_id, and the event_start time format are all documented in the schema. The description only adds the notion that contact and project can be combined; it says nothing about which attachment is required (only subject is required) or about the user_id/event_start defaults. 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?

Uses a specific verb ("add a note") plus the resource and the target entities (contact and/or project) in bexio, and the examples of note kinds (call log, meeting minutes, follow-up) pin down what a "note" is. No sibling tool creates notes, so the resource alone distinguishes it from the create_contact/create_invoice/create_timesheet siblings.

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 parenthetical examples imply when the tool fits (logging interactions and meetings), but there is no explicit when-to-use/when-not statement and no named alternative. For an additive write with no competing sibling, implicit guidance is adequate but thin.

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