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

Beyond annotations (readOnlyHint=false, idempotentHint=false, destructiveHint=false), the description adds two meaningful facts: the note author is the contact the API key belongs to, and 'Sends nothing' (no notification/email is triggered). This is real behavioral value. It stops short of describing failure modes or what happens if contact_id is invalid.

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 compact fragments with the operation type ('WRITE') front-loaded and no padding. The phrase 'Sends nothing' is slightly ambiguous (no email? no response body?) and would be clearer as 'sends no notification'.

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 simple three-parameter create tool with annotations and full schema coverage, the description covers author provenance, cardinality, and side-effect absence. The only gap is return behavior (e.g., whether a note id comes back) and error handling, which is minor given no output schema exists.

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 100%, so all three parameters are documented in the schema itself, giving a baseline of 3. The description only adds that the note attaches to 'a contact's record' and is authored by the API-key contact, which does not meaningfully extend the schema's per-field documentation.

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 note to a contact's record') and scopes cardinality explicitly with 'ONE', which distinguishes it from a bulk or list operation like civicrm_list_contact_notes. It also names the underlying API (APIv4 Note.create), so the agent knows exactly what entity is created.

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?

Usage is implied by the WRITE prefix and the contrast with the list_contact_notes sibling, but there is no explicit when-to-use/when-not guidance, no prerequisite about the contact existing, and no mention of permission or auth requirements. The 'APIv4 Note.create' hint gives implementation context but not selection guidance.

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