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

Annotations already declare this is a write (readOnlyHint=false), non-destructive, and idempotent, so the safety profile is covered. The description adds useful scope context (KRS + CEIDG sole proprietorships) but says nothing about auth requirements, duplicate handling, or what happens if neither key matches.

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 sentences, front-loaded with the core action, with no filler. Efficient, though the KRS/NIP detail slightly restates the schema.

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 simple, idempotent add with fully covered parameters and no output schema, the description is nearly complete. It omits only success/response behavior and error handling, which are minor given the annotations and schema already carry the operational profile.

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 krs and nip are already documented in the schema, including the 'used for CEIDG if no KRS match' note. The description paraphrases the same digit-length and entity-type details, adding marginal value, so the baseline of 3 is appropriate.

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?

States a specific verb and resource ('Add a company to the user's watchlist') and the identification keys, so it is clearly distinguishable from list_watchlist and remove_from_watchlist. It does not explicitly differentiate itself from the sibling add_watchlist_batch, leaving the singular-vs-bulk distinction to inference.

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 (this is the single-company add) but never stated explicitly, and the bulk alternative add_watchlist_batch is not named. No when-not or prerequisite guidance is given, though the KRS/NIP identification context is a small help.

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