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

With no annotations, the description carries the entire behavioral burden. It discloses that this mutates an existing record and that it 'Returns the updated tag,' which is useful given no output schema. However, it omits permission/auth requirements, whether unmentioned fields are preserved or cleared (partial-update semantics), and the uniqueness failure mode of name.

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?

Three tight sentences with the purpose front-loaded and no filler. Each sentence adds something (operation, trigger conditions, return value), though the structure is plain rather than notably well-organized.

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 straightforward 5-parameter update with no annotations and no output schema, the description covers purpose, when-to-use, and the return value, which is the key gap output_schema would otherwise fill. It is only missing behavioral detail (auth, partial-update semantics) for a mutation tool.

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 every parameter (id, name, color, icon, description) is already documented by the schema with formats and null semantics. The description only restates which fields are updatable (rename/recolor/icon/description) and adds no format or edge-case detail beyond the schema, so the baseline 3 applies.

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 ('Update an existing tag by ID'), so an agent immediately knows the operation. It does not explicitly differentiate itself from neighbors like create_tag, delete_tag, or update_category, but the resource noun makes the target 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?

'Use when the user wants to rename, recolor, or change the icon/description of a tag' gives clear, concrete trigger conditions. It stops short of stating when-not to use it or pointing to an alternative (e.g. delete_tag, assign_tags_to_transaction), so it lands at a solid 4 rather than 5.

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