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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), so the description is free to spend its words on content — and it does, listing the returned fields and noting it covers fixes for 'common ones,' which sets expectation that some codes may lack a fix. With no output schema, that enumeration is genuinely useful disclosure. It doesn't say what happens on an unknown/malformed code, which keeps it off a 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 sentences, zero filler, with the payload contents front-loaded ahead of the sourcing note. Efficient and easy to scan.

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 one-parameter read-only lookup with no output schema, the description supplies the return shape and honestly scopes fix coverage to 'common ones.' Missing only edge behavior — unknown code, case sensitivity — which is a minor gap given how simple the tool is.

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?

There is a single parameter and schema description coverage is 100%, including the HOST_NOT_AVAILABLE example, so the schema does the heavy lifting and baseline 3 applies. The description adds only the marginal hint that codes come from error responses, no format or casing guidance beyond the schema.

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 resource (a Claspine error code) and enumerates exactly what the answer contains: HTTP status, the messages it is raised with, where it is raised, and the fix. That is far more than a restatement of the title. It stops short of a 5 because it never distinguishes itself from the sibling check_code, which an agent could plausibly confuse with this lookup.

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 only implied: 'Every Claspine error response carries its code' tells the agent where the input comes from, which indirectly signals 'use this when you have an error code.' There is no explicit when-not, no prerequisite, and no mention of when to prefer api_reference or search_docs instead.

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