Add to your journal

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

Annotations only declare idempotentHint=false, so the description carries most of the behavioral burden — and it does: 'Nothing in the journal can be edited or deleted afterwards' clearly discloses irreversibility, which is the critical trait for a write tool. It omits size/length constraints and any indication of how entries are later retrieved.

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?

Two sentences, zero waste, with the core action and the content guidance front-loaded and the irreversibility caveat immediately after. Nothing to trim.

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 write tool with no output schema, the description covers purpose and the irreversible-append semantic well. It would be stronger if it acknowledged the structured 'data'/'tags' dimensions and pointed at journal_read for retrieving past 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 coverage is 67% (text and data are described, tags is not), so the schema does most of the work. The description adds no parameter-level information at all — it never mentions the structured 'data' payload or the 'tags' array, so an agent must read the schema to learn that structured detail or categorization is even possible.

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 ('Append one entry to your append-only journal') plus the content scope ('what you did, decided, or learned'). It does not explicitly distinguish itself from the nearby memory_write sibling, which is the main ambiguity an agent would face.

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 phrase 'what you did, decided, or learned' implies when the tool is appropriate, and the append-only framing suggests durable records. However, there is no explicit when-not guidance and no named alternative (e.g., memory_write for mutable notes, journal_read for retrieval), leaving the choice to inference.

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