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

Annotations only declare readOnlyHint, so the description usefully adds that no API key is required, which parsers/ecosystems it recognizes, and that the answer includes an example. It does not discuss response format details or limits, but the disclosure goes beyond the annotation.

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?

Front-loaded with the core action, then supporting detail about parser families and the no-API-key note; every clause carries information. The ecosystem list is dense but earns its place by setting expectations about recognized error formats.

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 single-parameter, read-only tool with no output schema, the description explains both the required input form and the shape of the answer (meaning, cause, fix, example), leaving nothing essential unspecified.

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 baseline is 3; the description adds real value by instructing the agent to include the stack trace prefix and paste the message verbatim rather than paraphrasing, which directly affects input quality.

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 ('Explain an XML parsing or schema validation error message') and enumerates the deliverable: meaning, cause, fix, plus an example. It is clearly distinguished from siblings like validate_xml (which produces errors) and explain_rule (which explains a rule).

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?

Gives clear input-side guidance ('paste the message as reported, stack trace prefix included') and names the parser ecosystems whose wording it understands, which tells the agent this is the right tool for any raw parser/validator output. It stops short of an explicit 'use X instead when...' routing statement against validate_xml or explain_rule.

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