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

Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, so the mutation profile is covered. The description adds that the response includes the new tab's sheetId, which is useful for subsequent calls. It doesn't discuss permissions or side effects beyond 'adding a tab,' but with annotations present, this is adequate.

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, front-loaded with the action and context, no filler. Every word earns its place.

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 mutation with annotations already covering side effects, the description covers the core need: what it does, when to use it, and what it returns. It doesn't discuss error conditions or required permissions, but those are not essential for this tool's complexity.

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 both parameters are documented in the schema. The description adds no additional parameter meaning beyond what's already in the schema, so 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?

The description states a specific verb ('Add'), a resource ('new tab'), and the target ('existing Google Sheet'). Combined with the name 'add_sheet_tab' and the phrase 'additional sheet after creation,' it clearly distinguishes this from create_spreadsheet and other sibling tools.

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?

Explicitly says 'Use this when you need an additional sheet after creation,' which gives a clear when-to-use context. It doesn't name alternatives or exclusion cases, but the scenario is specific enough for an agent to route correctly alongside tools like create_spreadsheet.

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