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

Adds real context beyond the annotations: the note becomes visible on the contact page and in get_contact_timeline, existing notes are immutable, and the return payload {id, content, createdAt} is spelled out. The description does not cover permission/auth requirements or rate limits, and it does not explicitly say the write is additive-only vs. destructive, but the immutability statement largely covers that.

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 the action and its purpose, then side-effect, then return value, then sibling routing in one compact paragraph. Slightly dense and the return-shape detail could be trimmed, but no sentence is filler.

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 two-parameter creation tool with no output schema, the description covers purpose, side effects and visibility, immutability of existing notes, return shape, and alternative tools. Nothing needed to call it correctly 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 coverage is 100% and both parameters are documented in the schema, so the baseline is 3. The description only loosely adds meaning by characterizing content as a remembered preference and pointing to where contactId comes from, which duplicates the schema's own note about using search (scope contacts).

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+resource (add a new note to a contact's record) and clarifies what a note is with an example. It explicitly distinguishes itself from update_contact (contact fields) and create_reminder, so an agent can separate it from the closest siblings without reading schemas.

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?

Gives explicit when-to-use ('a preference or detail the owner wants remembered'), when-not-to-use with named alternatives for both competing intents: update_contact for changing contact fields and create_reminder for reminders. Exclusions are concrete and route the agent correctly.

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