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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the agent knows this is a non-destructive write; the description adds the return contract (new tab's sheetId and title), which is genuinely useful. It does not disclose where the tab is placed, what happens if a tab with the same title already exists, or that headers occupy row 1 and shift data down. With the safety profile already covered by annotations, this is adequate but not rich.

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 short sentences, front-loaded with the action, then the disambiguation rule, then the return value. Every sentence carries information an agent would otherwise have to infer, and there is no filler.

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?

There is no output schema, and the description compensates by naming the returned fields (sheetId, title), which is the key missing piece. Combined with full schema coverage and the sibling contrast, an agent has enough to call it correctly; only edge-case behavior (duplicate titles, tab ordering, header row effects) is left unexplained.

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%, and every parameter (title, spreadsheet_id, account, headers) is documented in the schema itself, so the baseline is 3. The description adds no parameter-level meaning beyond the schema and never mentions the account or headers parameters, so it does not exceed the baseline.

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 ('Add a new tab (sheet) to an existing Google Sheets spreadsheet') with the clarifying parenthetical that disambiguates 'tab' from 'spreadsheet'. It also names the exact sibling it is not (sheets_create), so an agent can separate the two without opening either schema.

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 gives the selection rule: use sheets_create for a whole new file, use this to add a tab inside an existing one. That is clear when-to-use guidance with a named alternative. It does not cover the other plausible siblings in the same family (sheets_copy_tab_to, sheets_rename_tab, sheets_delete_tab), so the routing is clear but not exhaustive.

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