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

With no annotations, the description must disclose behavior. It states the tool is FREE and describes the output contents (countries, series IDs, etc.), which is helpful. However, it does not mention any side effects, pagination, or limits. The description also spends significant space on unrelated paid-tool receipt behavior, which does not clarify this tool's own behavioral profile.

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?

The description is excessively long and front-loads the core purpose but then diverges into unrelated details about paid answer tools, receipts, certified extracts, and other free tools. This is not concise and mixes multiple concerns, making it harder for an agent to quickly extract the essential information about this specific tool.

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 zero-parameter discovery tool with no output schema, the description adequately specifies what the agent can expect: a catalog with countries, series IDs, descriptions, freshness metadata, and URLs. It also notes the tool is free. The extraneous information does not leave gaps for calling this tool, though it could have omitted the unrelated receipt details to improve focus.

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 has zero parameters, so the baseline is 4. The description does not need to explain parameters. It adds no parameter semantics, but none are needed.

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 clearly states the tool is a free catalog of all euroref reference-data series, listing supported countries, series IDs, descriptions, freshness metadata, and URLs. It also instructs to call this first for discovery, effectively distinguishing it from siblings like get_series which fetch specific data.

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 description explicitly says 'Call this first to discover what data exists,' providing clear usage guidance. It also hints at alternatives by mentioning certified extracts are not MCP tools and verify_answer_receipt for receipts, though it does not systematically contrast with each sibling. This is sufficient for a discovery tool.

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