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

With annotations present (destructiveHint=false, readOnlyHint=false), the description adds valuable context beyond them: the split-type constraint (simple vs secure), and the browser redirect behavior for secure splits. This clarifies a significant behavioral limitation that annotations alone could not convey.

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, zero waste. The description front-loads the core purpose, then adds the scoping constraint and the browser caveat. Every sentence earns its place with no redundant phrasing.

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?

With an output schema present, the return shape is already documented. The description effectively covers the key operational constraint (split type) and the alternative path for secure splits. For a 2-parameter, low-complexity tool, this is well-covered. The only minor gap is that it doesn't mention what happens on failure (e.g., split not found).

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 50%, meaning the split parameter is documented in the schema but the name parameter has no description. The description mentions 'Add someone' which implies the name field's role, but doesn't elaborate on the split parameter's acceptable formats beyond what the schema already states ('split key, or whole link'). Baseline 3 is appropriate since the schema handles much of the documentation.

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+resource ('Add someone to an existing split') and clearly scopes functionality by distinguishing simple splits from secure splits, which are read-only here. It differentiates from siblings like remove_participant and rename_participant by naming the specific operation.

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 clearly states when the tool applies ('simple, accountless splits') and gives an explicit exclusion ('Secure splits... are read-only here and must be opened in a browser'). This provides strong context, though it doesn't name alternative tools for secure splits or mention other sibling alternatives in the same domain.

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