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

No annotations are provided, so the description carries the full burden. It mentions 'Requires write_mode', which hints at authentication or permission needs, but doesn't disclose other behavioral traits such as whether the update is reversible, potential side effects, rate limits, or what the output contains. For a mutation tool with zero annotation coverage, this is insufficient.

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 extremely concise—a single sentence that efficiently conveys the core purpose and a key requirement. It's front-loaded with the main action and resource, with no wasted words or unnecessary elaboration.

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?

Given that there is an output schema (which should cover return values), the description doesn't need to explain outputs. However, for a mutation tool with 3 parameters, 0% schema coverage, and no annotations, the description is too minimal—it lacks details on parameter meanings, error conditions, or broader context, making it incomplete for safe and effective use.

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 0%, meaning parameters are undocumented in the schema. The description adds no information about what 'variable_id', 'key', or 'value' represent, their formats, or constraints. It fails to compensate for the lack of schema documentation, leaving parameters largely unexplained.

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 states the action ('Update') and resource ('an existing instance variable'), which is specific and unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'create_variable' or 'delete_variable', though the 'existing' qualifier implies it's for modification rather than creation.

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 provides some context with 'Requires write_mode', which implies a prerequisite condition for usage. However, it doesn't specify when to use this tool versus alternatives like 'create_variable' or 'delete_variable', nor does it mention any exclusions or edge cases.

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