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

Goes well beyond the annotations: it discloses that validation and preview execute server-side, that the response bundles a match/change/exclusion report with per-field tallies, warnings and audit deltas, that the rule lands enabled and appended, and that it only takes effect on the next run. That is exactly the mutation behavior an agent needs and that readOnlyHint=false / destructiveHint=false does 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?

Front-loaded with the action and its most consequential behavior, then packed with distinct operational facts (report contents, human review, warning meaning, enabled state, ordering, next-run timing). No sentence is filler and nothing is repeated.

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 three-parameter mutation with no output schema, the description covers what is created, what is returned, how the returned report should be handled, and when the rule takes effect. An agent has everything needed to call and interpret it correctly.

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% and all three parameters are documented there, so the schema carries the load. The description's only parameter-relevant content, that the definition is validated and uses the same format as preview_rule, largely repeats what the schema already says for the definition property. Baseline 3 is appropriate.

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 ('Create a rule on a feed') and immediately bounds the scope: the definition is validated, a preview runs server-side, and the report comes back with the created rule. It is clearly distinguishable from preview_rule (no persistence) and delete_rule (removal) named among the siblings.

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?

Gives clear operating context: show the human the report, heed danger-level warnings, and know the rule applies on the next run rather than to the live feed. It also cross-references preview_rule for the definition format. It stops short of stating explicit exclusions such as 'use preview_rule first if you want to test without persisting', so no alternative-selection rule is spelled out.

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