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

Beyond the readOnly/destructive/openWorld annotations, the description discloses high-value behavioral facts: listing does not trigger legal delivery, opening a message legally counts as delivery, and content download via AI is impossible. This is exactly the kind of side-effect and constraint context an agent cannot get from structured fields.

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 tight sentences, front-loaded with what the tool returns before the constraints. Every sentence carries distinct information (fields, no-delivery side effect, content-download prohibition) with no filler.

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 read-only listing tool with annotations covering the safety profile and no output schema, the description supplies the return fields plus the crucial legal/behavioral caveats. An agent has everything needed to call it correctly and to know what it must not attempt.

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%, so both parameters (companyId, days) are already documented in the schema; the description adds no parameter syntax, defaults, or format detail. Baseline 3 applies when the schema carries the parameter burden.

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 a specific verb+resource ('Seznam OBALEK prijatych pisemnosti') and enumerates the returned fields (sender, subject, date, status), so an agent knows exactly what the tool produces. It does not, however, name or contrast any sibling tool (e.g. get_document), so sibling differentiation is only 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 a clear usage context ('Cteni seznamu NESPOUSTI doruceni') and a strong exclusion ('Stazeni obsahu zpravy pres AI neni mozne'), telling the agent that content retrieval must happen elsewhere. The alternative is described as a workflow ('v dashboardu'), not as a named sibling tool, so routing is clear but not tool-explicit.

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