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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses crucial behaviors: accounts with `code: null` genuinely lack a code and must be referenced by exact name, invented codes are rejected before proposal, and the connector has distinct fallback behaviors for authorising invoices. It also clarifies that taxType is only a hint and that archived accounts may be refused, all of which add significant non-obvious context.

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 long but each sentence earns its place by introducing a distinct caveat or rule needed for correct usage. It is front-loaded with the core purpose and read-only note, then progressively covers edge cases. Slight redundancy with the annotation's read-only statement and occasional wordiness prevent a perfect score, but the structure is clear and logical.

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 read-only list tool with one optional parameter and no output schema, the description is exceptionally complete. It covers how to handle null codes, how to use the results with invoice tools, when to omit accountCode, the taxType hint, and ACTIVE status preference. Everything an agent needs to call this tool correctly and integrate its output into downstream steps is present.

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 single optional `organisation` parameter is fully documented in the schema (100% coverage), and the description does not add any additional meaning about it beyond the schema. The description's 'This organisation's' wording implicitly references the current/default organisation, but the schema already explains when the parameter is needed, so the description provides no extra value here.

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?

The description clearly identifies the resource as 'This organisation's chart of accounts from Xero' and states the action explicitly as listing, with a specific read-only qualifier. It distinguishes itself from sibling create/update tools by emphasizing it is the source of truth for real account codes, and the title itself 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?

The description gives explicit when-to-use instructions: 'Use this BEFORE proposing an accountCode on a create_xero_invoice or update_xero_invoice line item,' and details what to do when no account fits, including omitting accountCode and letting the connector fill defaults. It also provides concrete alternatives for draft vs authorised invoices and warns about archived accounts, leaving no ambiguity about when to prefer this tool.

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