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

With no annotations, the description carries the burden and does well: it discloses partial-update semantics ('others stay'), atomicity ('all or nothing'), and a hard batch limit ('up to 500 a call'). It omits what the call returns (counts of updated vs added), permission/auth requirements, and what happens if the key column contains duplicates.

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 sentences, no filler, and the core matching semantics are front-loaded before the safety framing and the batch limit. Every clause carries information an agent needs to call this correctly.

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 mutation tool with no annotations and no output schema, the description covers semantics, atomicity, and batch limits, which is the bulk of what matters. The remaining gap is return/error behavior and permission prerequisites, which nothing else in the structured fields supplies.

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 coverage is 75%, so the schema already documents all four parameters; the description still adds value by giving a concrete key example ("Email") and implying the key column must be unique. It says nothing about the rows payload shape beyond the 500 cap, and table/workspace are left entirely to the schema.

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 precise verb-and-resource with its exact semantics: 'update-or-add by the table's unique column', spelling out that matched rows get the given cells set while the rest are inserted. That distinguishes it in substance from add_rows/update_rows, though it never names those siblings, so an agent must infer the boundary rather than read it.

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 safe way to keep a registry in step without making duplicates' gives a clear usage context that selects this tool over a plain insert. It offers no explicit exclusions or named alternatives (e.g. 'use add_rows when you know every row is new'), leaving the negative case implicit.

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