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

Annotations already declare not-read-only, non-destructive, and closed-world, so the safety profile is covered. The description adds what the annotations cannot: the note is appended (additive), appears on the contact's timeline, and is visible in the CRM to members. It does not mention permissions or how existing timeline entries are affected, which a mutation tool could clarify.

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?

One front-loaded sentence: the action and target come first, followed by visibility and use cases. No filler and no repetition of the title or schema.

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?

With an output schema, annotations, and full parameter coverage, the description only needs to convey intent and effect; it does both by naming the timeline and its audience. Minor gaps remain on required permissions and how notes interact with existing timeline entries.

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%: the contact_id and content parameters are fully documented in the schema, including that content is plain text up to a few paragraphs. The description adds no parameter detail beyond that, so the baseline of 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?

Specific verb and resource: 'Append a note to a contact's timeline.' It is clearly distinct from add_tag, update_contact, and send_email because it describes a timeline note rather than a tag, a field update, or an email. An agent can route to this tool without opening another schema.

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 intended use cases (handoffs, call summaries, member-visible context), which implies when to call it, but it never states when not to call it or names an alternative such as update_contact for structured data or add_tag for labeling.

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