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

Annotations already indicate readOnlyHint=false and destructiveHint=false. The description only says 'Add', which is implicit from the tool name and annotations. It does not disclose additional behavior such as validation of the parent entry, effect on totals, or failure modes. No extra transparency beyond the annotations.

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?

The description is two concise sentences, front-loading the core purpose and immediately providing sibling context. No wasted words.

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 mutation with 5 clear parameters, the description provides enough to understand the operation. However, it omits any mention of parameter requirements (all are listed optional in schema) and does not explain return behavior or error conditions. Adequate but not fully complete.

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?

The schema descriptions already cover each parameter with 100% coverage, so the description adds little. It does not clarify that entryid, accountid, and one of debit/credit are logically required even though the schema lists no required parameters. This is a minor gap but not severe given the parameter descriptions.

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 action ('Add a line') on a specific resource ('existing journal entry') and clearly distinguishes from sibling tools by naming update_journal_line and save_journal_entry. The purpose is unambiguous.

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 tells when to use this tool versus update_journal_line (pairs with) and save_journal_entry (for whole new entry). It does not cover other potential alternatives or prerequisites, but the given guidance is clear and actionable.

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