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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful return-shape context with no output schema, but it lists "the paper's general marking principles" as returned content while the schema defaults include_principles to false, which can mislead, and it says nothing about behavior for an unknown part id or paper.

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?

It is a single front-loaded sentence with no filler, and every clause documents a distinct returned field. The long enumeration of row fields makes it slightly dense to scan, but nothing is redundant.

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 return values and does so thoroughly: row codes, marks, answer, guidance, alternatives, part maximum, principles, PDF page and link. Only failure behavior and the paper_id source (covered in the schema) are unaddressed.

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%, so paper_id, part and include_principles are already documented with formats and an example, and the description adds no syntax or constraint detail beyond that. The clause about marking principles loosely maps to include_principles but does not clarify the default behavior, so the baseline of 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?

States a specific verb and resource ("official mark-scheme rows") and narrows scope precisely to "one part of an exam.now past paper", so the granularity is unambiguous. It does not name a sibling or state how it differs from get_question or mark_answer, which keeps it short of a 5.

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?

There is no explicit when-to-use or when-not-to-use guidance and no mention of alternatives such as get_paper or mark_answer. The only usage signal is implicit in the phrase "for one part of an exam.now past paper", leaving the agent to infer the workflow context.

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