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

readOnlyHint=true already establishes this as a safe read, so the description only needs to add context; it does add the id-precondition and the returned field set. It says nothing about behavior for an invalid/missing id or what the response envelope looks like. Useful but not rich beyond the annotation.

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?

Two short sentences, the resource and return shape front-loaded, no filler. The trailing endpoint string is mildly noisy but negligible.

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 one-parameter read, the description plus readOnlyHint covers what an agent needs: what it fetches, which fields return, and where the id originates. No output schema exists, but the field enumeration substitutes adequately.

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 100% and the single param is already documented. The description still adds value by stating the id's provenance (search or autocomplete), which is not in the schema and tells the agent where a valid value must come from.

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 ('One reminder by id') and enumerates the returned fields (description, date, remindee, completion state, linked records), so an agent knows exactly what it gets. It does not explicitly name rex_search_reminders as the alternative, but the id-provenance sentence implies the split.

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 id comes from a search or autocomplete' tells the agent this is a follow-up call and points at the sibling family that produces ids. No explicit when-not or fallback behavior is given, which keeps it short of a 5.

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