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

Annotations already declare readOnlyHint=false and idempotentHint=false; the description adds genuinely new behavior: 'Not retried' (critical for a caller deciding whether to re-attempt) and 'Returns the new note id'. It does not explain what happens if both contact_ids and property_ids are omitted, which would be useful given the destructiveHint=true flag.

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 with the operation class first, followed by the non-retry/return/endpoint facts. Every clause carries information; nothing is repeated from the 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 no output schema, the description helpfully states the return value ('the new note id'), and the non-retry note covers the main failure-handling question. It is slightly incomplete on the required-vs-optional targeting rule (whether a note with no contact or property is valid) for a 5-parameter mutation.

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%, so every parameter is already documented in the schema; the baseline of 3 applies. The description only reiterates that notes can target multiple contacts and/or properties, adding no format or constraint detail beyond the schema (e.g. the 20-item cap or note_type value-list lookup).

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 ('add a note') plus the exact resource scope ('to one or more contacts and/or properties'), which cleanly separates it from rex_get_note and rex_search_notes. The 'WRITE:' prefix makes the operation class immediately legible.

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?

Provides concrete usage contexts ('after a call or an open home') that tell an agent when this tool is appropriate. It does not name a competing alternative or state exclusions (e.g. when to use search_notes instead), so it stops short of a full routing rule.

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