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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful behavior beyond that: it names the returned fields (EMA summary, authorisation status, ema_url) and points to where the SmPC lives on the returned page.

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 tight sentences, both earning their place, with the scope and the exclusion front-loaded. Slightly telegraphic alongside the title but not wasteful.

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?

An output schema exists, so return values need not be spelled out, yet the description still usefully flags the key fields. Combined with the annotation coverage and the name-vs-substance note, an agent has enough to call the tool correctly.

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?

With 0% schema description coverage the description must carry the param burden, and it does explain the key 'name' parameter by stating it accepts either a brand name or an active substance. The 'limit' parameter is left entirely undiscussed, so compensation is only partial.

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 the specific resource (centrally authorised EU medicines) and the lookup key (brand name or active substance), and explicitly excludes nationally authorised medicines. It is clearly separable from lookup_pubmed and search_evidence_library, though it relies on the name/title for the verb 'lookup' rather than stating an action directly.

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?

Provides a concrete when-not: nationally authorised medicines are absent from this register and the agent should consult the national agency instead. This is a real selection constraint, but it does not route the agent to any of the sibling tools for adjacent query types.

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