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

Annotations already declare this is a non-destructive, non-idempotent, closed-world write, so the safety burden is partly lifted. The description adds that the new entry is grouped with the original, which is useful behavioral context beyond the annotations. It says nothing about permissions, limits, what fields the copy inherits, or how the caller obtains the new entry's identifier.

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 of roughly equal weight, both earning their place: the first defines the operation and its purpose, the second routes the agent to the correct follow-up tool. Nothing is padded and the key fact is front-loaded.

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, the description covers purpose, outcome and follow-up. However there is no output schema, and the description never says what the call returns — notably the new photo's identifier, which the caller needs before the recommended update_photo step. That gap is the one thing a fully complete definition would close.

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 only 50%: 'site' is documented in the schema but 'photoId' has no description anywhere. The description text mentions no parameters at all, so it does not compensate for the gap — an agent gets no help identifying which photo is being duplicated or what constraints apply.

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 gives a specific verb and resource ('Copies a bank entry') plus the business rationale ('a second colour, size or stage of the same product'), and explicitly names update_photo as the tool that handles subsequent edits, which separates it from the sibling it is most easily confused with. The only friction is that it calls the resource a 'bank entry' while the tool name and siblings talk about 'photo', forcing a small inference.

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 'when' is stated concretely: use it when a second colour, size or stage of the same product is needed, so the copy stays grouped with the original. It also names the follow-up step ('Edit the copy with update_photo afterwards'), which is genuine sequencing guidance. There is no explicit 'do not use this for...' exclusion, so it falls short of a 5.

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