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

Annotations already declare readOnly, idempotent, non-open-world, non-destructive, so the safety profile is covered. The description adds two things the annotations do not: that the call is free (relevant given buy_credits/get_balance siblings) and that the returned glossary is automatically enforced on transcribe/translate — real behavioral context. It stops short of describing response shape or empty-state behavior.

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 sentences, zero waste. The cost signal ('Free.') is front-loaded, followed immediately by what the resource contains, and the last sentence carries the one behavioral fact that matters. Nothing is repeated from the title or annotations.

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 parameters and no output schema, the description carries the burden of describing the return value, and it does so semantically by enumerating the glossary's entry types. Adequate for a zero-arg read; only the concrete response field names and empty-glossary behavior are absent.

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?

Zero parameters, so the baseline is 4. The description nonetheless clarifies the scope of the implicit target — the glossary belongs to 'this account (or key)' — which tells the agent the result is scoped to its credentials rather than globally addressable.

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?

Names a specific resource (the saved glossary of this account/key) and enumerates its contents — preferred spellings, brand names, alias fixes, do-not-translate terms — so the agent knows exactly what comes back. The verb is only implied by the name rather than stated in the description, and no sibling (save_glossary, delete_glossary) is explicitly contrasted, which keeps it from a 5.

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?

Usage is implied rather than stated: by saying the glossary 'is applied to every transcribe and translate automatically,' it hints the agent should read this to know what corrections will be applied. It never says when to call it, whether it is a prerequisite to anything, or how it differs from other read tools like list_presets or get_custom_preset.

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