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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds real value by disclosing the data source ('From the token reply of POST /connect/token'), which implies this reflects credential scope rather than a paged API listing. It does not discuss result size or error behavior, keeping it below 5.

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 dense sentences with no filler; the purpose and returned fields are front-loaded, and the operational hint about company_id follows immediately. Every clause earns its place.

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-param read tool with no output schema, the description compensates well by naming the four returned fields and the source of the data. It could still say whether the list is always complete or scoped by environment, but nothing essential for correct invocation is missing.

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 takes zero parameters, so the baseline is 4. The description still helps by naming the downstream argument (company_id) these values feed, clarifying how the output is consumed even though there is nothing to parameterize here.

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+resource ('List the companies') and enumerates the returned fields (id, code, name, group), plus the access scope ('the API credentials can access'). The note that company ids feed the company_id argument of the other tools makes its role distinct from the many payspace_list_* siblings.

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?

'Company ids go into the company_id argument of the other tools' effectively tells the agent to call this first as a prerequisite for the rest of the toolset. It gives clear context but no explicit exclusions or alternatives, so it falls short of a full when/when-not statement.

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