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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds value beyond that by enumerating payload contents (description, page images, PDF, and an editorial correction when present), which tells the agent to expect nullable sub-resources rather than a uniform record.

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?

A single compact sentence with the identifying key front-loaded and the return payload enumerated after the colon. Nothing is wasted, though the fragmentary phrasing costs it the top mark a clear verb would earn.

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?

With no output schema, the description carries the burden of describing what comes back, and it does so adequately for a two-parameter read. The conditional 'when there is one' flags that the correction field is optional, which is the main behavioral nuance an agent needs.

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%: the id parameter is documented as coming from search_exam_papers and lang is documented with its enum and default. The description only echoes 'by id' and says nothing about the lang parameter, so it neither adds nor detracts; baseline 3 applies.

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?

Names the resource (a single past exam paper) and the key (by id), and the singular framing distinguishes it from the sibling search_exam_papers. It is written as a noun phrase rather than a verb phrase, so it never literally states 'retrieves', but the intent is unambiguous.

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?

'By id' plus the schema note pointing at search_exam_papers implicitly tells the agent this is the fetch-after-search step. There is no explicit when-to-use, when-not-to-use, or named alternative in the description itself, so the routing is inferred rather than stated.

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