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

The annotations already declare readOnlyHint=true, covering the safety profile. The description adds useful context by naming the return payload (contacts, address, balance, paid-to-date), which goes beyond the annotations. It does not disclose error behavior, permissions, or rate limits, so it remains at a moderate level.

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?

The description is two sentences with no wasted words. The first sentence front-loads the purpose and returned fields, while the second provides the API endpoint mapping. It is appropriately sized for a simple getter.

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 read-only getter with 100% parameter coverage and a readOnlyHint annotation, the description is complete enough. It names the returned fields, compensating for the lack of an output schema. Nothing an agent needs in order to call it correctly 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?

Schema description coverage is 100%, and the single parameter client_id is fully documented with a hashed ID example. The description adds only 'by id', which does not provide syntax or format details beyond what the schema already offers. The baseline of 3 is appropriate when the schema does the heavy lifting.

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 states a specific verb and resource: 'Fetch one client by id.' It also lists returned fields (contacts, address, balance, paid-to-date), making the purpose clear. However, it does not explicitly differentiate itself from siblings like list_clients, create_client, or update_client, so it falls short of the top score.

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 no explicit guidance on when to use this tool versus alternatives such as list_clients or get_invoice. The phrase 'by id' weakly implies retrieval of a known client, but there is no stated condition, exclusion, or alternative tool to route the agent.

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