fetch

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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false), so the bar is lower. The description adds genuine value beyond annotations: 'verified public document' scopes the data source, 'when available' warns of potentially incomplete attribution/dates, and 'never infer a review' is a strong behavioral constraint against fabricating content. No contradiction with annotations - 'Fetch' aligns with readOnlyHint=true.

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 with zero waste. The primary purpose is front-loaded in the first sentence, the second covers return values and constraints. Every clause earns its place; nothing is redundant with the schema or annotations.

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 1-parameter tool with an output schema present and strong safety annotations, this is complete. Return content ('source text, attribution and dates') is summarized without duplicating the output schema. Minor gaps: no statement about behavior when an ID is not verified or not found, and no error-handling guidance.

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 0% - the single 'id' parameter has no description in the schema, so the description must compensate. It does: 'canonical URL ID returned by search' precisely defines the parameter's source and format. This is meaningful semantic information the agent would otherwise lack.

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 ('Fetch') and resource ('a verified public document') with a clear provenance constraint ('canonical URL ID returned by search'). The 'never infer a review' clause sharpens what the tool does not do. It is distinguishable from sibling 'search' (which finds IDs) and 'mrx_read_page' (page reading) without opening schemas.

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 phrase 'returned by search' clearly implies this tool is invoked after search has produced an ID, giving contextual guidance. However, with six siblings present, it does not explicitly name alternatives or state when NOT to use it (e.g., no exclusion against mrx_read_page or mrx_get_started). Usage is implied rather than explicit.

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