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

The only annotation is destructiveHint=true, so the description carries most of the behavioral burden. It adds the 'contact's timeline' placement, which is useful, but says nothing about permissions, whether the note can later be edited/deleted, or why the operation is flagged destructive — surprising for an append-style note.

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 with the action front-loaded and no filler. The endpoint string is marginally useful for API mapping but adds little for an agent deciding whether to call the tool.

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 mutation tool with no output schema and fully documented parameters, the essentials are present. However, the description omits authentication/scope requirements and any side effects, leaving behavioral gaps that annotations alone do not fill.

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%, with all four parameters (personId, body, subject, isHtml) documented inline, so the baseline is 3. The description adds no additional syntax, formatting, or length-constraint detail beyond the schema.

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 with scope: 'Add a note to a contact's timeline,' plus the underlying endpoint. It is clearly distinguishable from list/get/update siblings, though it names no alternatives explicitly to sharpen the boundary.

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?

There is no when-to-use guidance, no prerequisites (e.g., person must exist), and no mention of alternatives such as fub_log_call or fub_send_lead_event for related timeline entries. The agent must infer usage from the name alone.

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