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

Well beyond the annotations (readOnlyHint=false, destructiveHint=false), it discloses that Expensify posts an 'added a receipt' message, that the action is effectively non-blocking ('does not wait for your OK'), that an Approved report requires a Workspace Admin or the call fails with a role error, and that a Cotlet API key with app access is needed.

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?

Front-loads the purpose, then layers side effects, permissions, and auth. Mostly earns its length, though the sentence 'It reaches no one and you can replace the file in Expensify, so it does not wait for your OK' is a bit compressed and slightly ambiguous.

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 mutation tool with no output schema, it covers the key gaps: the return value (receipt link), the side effect (posted message), the non-blocking behavior, the admin permission constraint on Approved reports, and the auth requirement. An agent has everything needed to invoke it correctly.

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 description coverage is 100%, so expense_id, receipt_url, and the replace flag are already documented in the schema. The description reinforces the replace semantics but adds no new syntax or format detail beyond the structured fields.

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: adds a receipt image/file to an expense, or replaces the existing one. It is easy to distinguish from siblings like expensify_get_expense or expensify_create_expense because the action (attach a file to an existing expense) 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 clearly frames the two attach vs. replace cases and notes the replace constraint, and calls out the Approved-report admin requirement. It does not name a sibling alternative, but the context for when the tool applies is clear.

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