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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the 'Read-only' sentence in the description is largely redundant with structured data. The genuine added value is the disclosure of what the payload contains (level, word count, finished materials, status breakdown), which matters since no output schema exists — but permission/auth and profile-missing behavior remain unstated.

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?

Three short clauses: what it returns, when to call it, and its safety profile — all front-loaded with zero filler. Nothing could be removed without losing information.

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-optional-parameter, read-only lookup with no output schema, the description covers purpose, timing, and returned fields adequately. The only missing element is behavior when no profile exists for the requested language, which is a minor gap given the schema's documented default.

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 optional parameter already documents its format example ('en') and its default behavior (falls back to the caller's only profile). The description adds nothing about the language argument, so the baseline 3 applies.

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 (the caller's profile for one language) and enumerates what it returns: estimated level, known-word count, materials finished, and status breakdown. That is concrete and distinguishable from write-side siblings like language_add_material or language_answer, though it does not explicitly contrast with read siblings such as language_get_readiness.

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?

'Use at the start of a session to know who you are teaching' gives a clear triggering context, which is exactly the guidance an agent needs for a session-bootstrap read. It stops short of naming alternatives or exclusions (e.g., when to prefer language_get_readiness), so it is clear context without full routing.

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