Note something about a contact

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

Beyond the annotations (which only declare it is a non-read, idempotent, non-destructive write), the description adds high-value behavior: the note is stored on this machine only, nothing is sent to WhatsApp, the contact never sees it, and it propagates to five named tools. These are exactly the traits an agent cannot infer from structured fields.

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?

Front-loaded with purpose, then effect, then privacy, then removal — a logical order with no filler sentences. The inline quoted examples are slightly informal in formatting but earn their place by demonstrating note format.

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 3-parameter tool with full schema coverage and no output schema, the description covers everything an agent needs: local-only scope, cross-tool visibility, privacy, and removal. Nothing material is missing.

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 already documented in the schema, including the empty-string removal semantics. The description's examples of note content add mild meaning but do not go beyond what the schema provides, 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?

The description states a specific verb and resource (remember/set a note about a person) and immediately differentiates itself by explaining where the note surfaces (list_chats, search_contacts, get_contact, get_recent_messages, get_unanswered). This lets an agent distinguish set_contact_note from sibling read tools without opening any 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?

It gives concrete context for use via examples ("the accountant", "always answers late") and states the removal condition for empty notes. There is no explicit when-not or named alternative tool, but no sibling competes for this function, so the guidance is clear without exclusions.

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