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

The annotations already declare destructiveHint=true and readOnlyHint=false, so the write risk is covered. The description adds a genuinely useful precondition (old must be unique unless replace_all), but leaves open what happens on zero or multiple matches — error, no-op, or partial write — which matters for a destructive mutation.

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 short sentences, the core swap semantics front-loaded and the precondition immediately after. No padding, and the backticked parameter names make the mapping to the schema instant.

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 destructive mutation with no output schema, the definition covers the match precondition but omits failure behavior and whether the change is undoable or requires a prior read. The annotations carry the risk profile, so the remaining gap is moderate rather than critical.

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 only 25%, so the description has to carry weight, and it does: it defines old as an exact literal that must match uniquely and explains replace_all as the escape hatch for multiple matches. Only new is left implicit, which is the least ambiguous of the four.

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 action (exact string replacement) on a specific resource (index.html), which clearly separates it from landing_write_page's full-page write. It does not name the sibling explicitly, so it falls just short of 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?

Usage is implied rather than stated: an agent can infer this is the targeted, surgical edit path used instead of landing_write_page, but the description never says 'use this when editing a small section' or names the alternative.

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