Subscribe to a URL user rule

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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false) by disclosing the validate-before-enable flow, disallowed URL forms (redirects, credentials, queries except a Git ref), the auth_env bearer-token mechanism and the AGENTS_RULE_AUTH_HOSTS binding requirement, the granted scope, the security note that sources are not system instructions, and the absence of background refresh.

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 core action and dense with constraints, almost every clause earning its place. A few fragmentary run-ons (the metadata and auth_env lines) require re-reading, so the structure is efficient but not maximally clean.

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, return values need not be described, and annotations already cover the safety profile. The description supplies the remaining essentials — validation, URL restrictions, auth wiring, granted scope, and refresh behavior — leaving nothing an agent needs in order to invoke 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 description coverage is 0%, so the description must carry the load, and it does: it constrains 'url' (HTTPS, raw, no redirects/credentials/queries except a Git ref) and explains 'auth_env' names a server env var used as a Bearer token while warning never to pass the token itself. The 'Git ref parameter' phrasing is slightly ambiguous, so it falls just short of fully compensating.

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 — 'Subscribe to one HTTPS raw MDC rule' — and pins the scope to a single rule enabled as user:<frontmatter name>. This is clearly distinct from the refresh/get/set_enabled/rollback/delete siblings in the user-rule family, so an agent can route without opening the 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?

'Subscribe ... when the user requests it' gives a triggering condition, and 'No automatic refresh or background polling' implicitly separates this from refresh_user_rule. It stops short of explicitly naming the sibling alternatives or stating when NOT to subscribe, so it is clear context rather than full when/when-not guidance.

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