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

With no annotations, the description must carry the behavioral burden. It discloses that the operation is a read-only 'check' and that it requires no account, which is useful. But it does not describe what the tool returns, whether verification success/failure is signaled in a particular way, or any side effects, leaving the agent partially in the dark.

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 with no filler. The purpose is front-loaded, and the invocation alternatives and auth note each earn their place. The description is well-sized for the tool's simplicity.

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 four-parameter, no-required-fields verification tool, the description covers the essential usage patterns and the access requirement. The main gap is the absence of any statement about what the check returns or how results are formatted, which matters more since there is no output schema. Still, the core selection and invocation knowledge is present.

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 coverage is 100%, so the baseline is 3. The description adds real semantic value beyond the schema by explaining the either/or relationship: supply agreement_id, or paste the trio of canonical text, signature, and public key from a copy. This resolves the schema's ambiguous 'Or:' phrasing on the canonical parameter.

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 opens with a specific verb and resource: 'Check a Focxle agreement has not been changed.' This clearly identifies the operation as integrity verification, which is distinct from sibling tools like agreement_get or agreement_confirm_paid. The alternative invocation modes (agreement_id vs pasted copy) further sharpen the purpose.

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 gives clear usage context: 'Give its agreement_id, or paste the canonical text, signature and public key from a copy somebody sent you.' This tells an agent how to invoke it, and the 'no account needed' note clarifies access. However, it does not explicitly name when to prefer this over siblings like agreement_get, so it stops short of a full 5.

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