Write a journal note

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

Annotations already declare a non-destructive write (readOnlyHint=false, destructiveHint=false), and the description adds real value on top: it explains why it never overwrites (days hold any number of notes), states the return value, and discloses the OAuth/LuxAlgo sign-in requirement. Auth prerequisites are exactly the kind of context annotations don't carry.

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?

Three tight sentences, front-loaded with the core action, followed by the non-overwrite guarantee and the routing alternatives. No filler or repetition; every clause carries information.

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 simple two-parameter write tool, the description covers the action, the non-destructive guarantee, the alternatives, the return value, and the auth requirement. With no output schema, noting that it returns the note with its id is a helpful touch.

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 already documented with format and timezone. The description repeats the YYYY-MM-DD/journal-timezone constraint but adds no syntax or edge-case detail beyond the schema, so the baseline 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?

States a specific verb and resource ('Add a new note to a trading day') and immediately distinguishes itself from journal_update_note and journal_update_trade's notes. An agent can tell what this does and what it doesn't do without opening the 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?

Explicitly names both alternatives and the condition that selects each: use journal_update_note to change an existing note, and journal_update_trade's notes for a trade-specific note. It also clarifies the day can be traded or not, removing ambiguity about applicability.

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