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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the tool is safe. The description adds behavioral context: results are ordered by view count and perform exact substring matching. This goes beyond annotations, but could mention default behavior on empty queries or case sensitivity.

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?

The description is two sentences, each with clear information. The first sentence packs the core purpose and ordering, while the second reinforces usage context. No unnecessary words, fully front-loaded.

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?

Given the tool's simplicity, an output schema exists (so return values need no elaboration), and the description covers what, how, and when. Could mention pagination or default ordering, but not essential for a low-complexity tool.

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 the schema fully documents both parameters. The description adds the context of 'exact substring lookup' which reinforces the query parameter's purpose, but does not provide additional details beyond what the schema already conveys. Baseline 3 is appropriate.

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?

Description clearly states 'Exact substring lookup over thread titles and author usernames, ordered by view count' with a precise verb phrase and resource scope. It explicitly distinguishes from the main 'search' tool by noting 'literal title or author matching rather than relevance-ranked full-text search', effectively differentiating from siblings.

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 description gives clear guidance: 'use this for literal title or author matching rather than relevance-ranked full-text search' and notes it 'Complements the main `search` tool'. However, it does not explicitly list alternative tools or conditions when not to use, though the sibling context implies options.

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