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

Annotations already establish readOnly/idempotent/non-destructive, so the description correctly does not contradict them. It adds real value beyond the structured fields by decoding the semantics of the payload: level is self-assessed A1-C2, mode is strict/zen/mix chosen per session, advance is a delay in seconds with 0 meaning manual, and pace lives in today() rather than here.

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?

It is one long run-on paragraph stitched together with semicolons, and nested details such as the purpose variants and the advance units are buried mid-sentence. Every clause carries information, but the flat formatting makes it slower to parse than a bulleted field list would be.

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 no output schema and no parameters, the description carries the full burden of describing the return shape, and it does so field by field, which is exactly what an agent needs. The remaining gap is edge behavior: what is returned when no active language profile exists is not stated.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate on the input side. The field glossary it does provide is orthogonal to the (empty) schema rather than redundant with it.

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 names the resource precisely (the learner's profile in the active language) and even enumerates its fields, so an agent understands it is retrieving the profile object. But it never uses a verb like 'get'/'return' and never mentions profile_update, so the read-vs-write distinction from its closest sibling is left implicit.

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?

It gives no guidance on when to call this versus profile_update, today, progress or plan, all of which touch adjacent data. There are no exclusions, prerequisites, or timing hints; the agent is left to infer usage entirely from the resource name.

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