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

Annotations already flag destructiveHint=true and readOnlyHint=false; the description goes well beyond that by explaining PATCH semantics (omitted fields unchanged, null clears an override and restores pool inheritance), whole-object replacement for overlays/metadata, and the key consequence that existing machines keep their config while new launches pick up the new defaults/limits. It does not cover permissions or reversibility, so it lands just short of the top.

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?

Four tightly packed sentences, each carrying a distinct rule (scope, PATCH semantics, replacement semantics, effect on existing vs new machines), with the core action front-loaded. No filler or restatement of the tool name.

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 19-parameter mutation with nested objects and no output schema, the description covers the hard parts: partial update semantics, inheritance clearing, and how changes propagate to machines. It is let down slightly by not mentioning authorization scope or what the call returns, but the behaviorally risky aspects are all addressed.

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 100%, so the baseline is 3, but the description adds genuine meaning the schema does not: the general omitted/null/cleared-override contract and the fact that overlay objects and metadata are replaced whole rather than merged. That materially improves how an agent would populate the nullable limit and overlay parameters.

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 opens with a specific verb+resource: 'Updates the grant's overrides and limits.' Combined with the tool name, an agent can immediately tell this is a mutation of an existing machine-pool grant rather than a get/list/add/delete operation, and 'overrides and limits' accurately scopes what is being edited.

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 implies this is the tool for changing an existing grant and even explains inheritance behavior relative to the pool, but it never states when to pick it over grant_pools_add/delete or grant_models_edit, nor any preconditions or exclusions. Usage is inferable rather than explicit.

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