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

Annotations already declare readOnly/idempotent/non-destructive/open-world, so safety is covered. The description adds genuinely new behavioral context beyond annotations: the count is a hard budget and results are not a complete or unbiased survey, warning the agent about sampling limits.

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?

Three tight sentences with the core purpose front-loaded and no filler. Each sentence carries distinct information: what is read, the budget caveat, and the continuation path.

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 usefully enumerates what comes back (links, parent IDs, coverage, next_links). The main gap is the undocumented parameters, but for a read-only retrieval tool the behavioral picture is otherwise complete.

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 0% across 4 parameters, so the description must compensate, and it largely does not. It alludes to maxComments via 'the count is a hard budget' but never explains url, sort, or maxDepth, leaving the agent to infer all parameter meaning from bare schema types.

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 (read) and resource (a Reddit post and its loaded comments), plus the shape of the return (original links, parent IDs, coverage). It implicitly distinguishes itself from reddit_search by fetching a single post rather than searching, though it never names the siblings explicitly.

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 closing line 'Follow next_links for more threads' gives real continuation guidance for paginating, and the budget caveat implies when results are partial. However, it never states when to prefer this over reddit_search or x_post, leaving alternative selection to inference.

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

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

Annotations already declare read-only, idempotent, open-world behavior, so the safety profile is covered. The description adds genuinely new behavioral context: cursor lifetime is session-scoped to 15 minutes and filters must remain stable across pages, which is not derivable from the schema or annotations.

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 tight sentences with zero filler: purpose first, then the pagination constraint. Every clause carries information the agent needs.

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 6-parameter search tool with no output schema and 0% schema coverage, the definition covers purpose and cursor behavior but omits the semantics of the filtering and sorting parameters that materially change results. Annotations carry the safety profile, so the remaining gap is parameter 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 description coverage is 0% across 6 parameters, so the description must carry the burden. It explains cursor semantics well but leaves sub, sort, time, and limit completely undocumented, and the enum members for sort/time are only visible in the raw schema with no explanation of their meaning.

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+resource ('Search Reddit') and adds a distinguishing detail ('original ordering and canonical links') that separates it from the x_* siblings. It never explicitly contrasts itself with siblings like reddit_post, so it falls 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?

Provides real paging guidance ('cursor is valid only within this server session for 15 minutes; keep query and filters unchanged when paging'), which tells the agent how to iterate correctly. However, it says nothing about when to pick this over reddit_post, x_search, or x_post, so usage context is only partially covered.

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

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

Annotations already declare the read-only, idempotent, non-destructive profile, so the bar is lower, yet the description adds real traits beyond them: it reports missing IDs rather than failing, explicitly does not expand full reply threads, and discloses per-returned-post billing. That cost and missing-ID behavior are genuinely useful and not inferable from the annotations.

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?

Three short sentences, front-loaded with the core action and progressively adding scope, exclusion, and cost. No sentence is redundant and nothing is buried.

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 usefully characterizes the response (includes quotes and reply references, reports missing IDs). Cost and scope limits are covered. It is only slightly incomplete in not describing the compact/full detail tradeoff at a level beyond the schema's own text.

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 50%: the detail enum is self-documented in the schema, while ids has no schema description beyond its numeric pattern. The description says 'numeric ID' but adds no meaning about batch size, format, or what compact vs full actually returns, so it does not compensate for the coverage gap. 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?

States a specific verb (Read) and resource (X posts) with the exact lookup key (numeric ID) and even names the data provider (TwitterAPI.io). The 'by numeric ID' qualifier cleanly separates it from the sibling x_search, which is for discovery rather than direct ID retrieval.

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 'by numeric ID' framing clearly implies the precondition (you already have post IDs), and 'does not fetch a full reply thread' is an explicit scope exclusion that prevents misuse. It stops short of naming x_search as the alternative for ID discovery, so it isn't a full when/when-not routing statement.

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

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds meaningful traits beyond them: per-post billing, a ~20-post page size, preserved Latest/Top ordering, retained reply/quote context, and the absence of automatic retries or popularity filters. Error-handling and rate-limit behavior beyond 'no retries' is left unstated, so not a full 5.

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?

Four compact sentences, front-loaded with the purpose and return shape, each carrying distinct information (source, page size, ordering, billing, paging, retry policy). Slightly dense but no filler.

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 correctly carries the return-value burden by describing page size, ordering preservation, and included reply/quote context. What remains thin is guidance on query construction and how cursor paging terminates, which a low-coverage schema does not cover.

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 only 25% (only 'detail' is documented), so the description must compensate and partly does: it explains ordering via the Latest/Top mention and paging via the cursor. However, it refers to 'next_cursor' while the actual parameter is named 'cursor', and it never characterizes the required 'query' parameter's syntax or the compact/full tradeoff.

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 ('Search X through TwitterAPI.io') and describes the return shape ('one whole upstream page... up to 20 posts'). An agent can immediately distinguish this from reddit_search and x_post without opening any schema.

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?

Gives operational context ('Pass next_cursor to page') but never states when to choose this over reddit_search or x_post, nor any exclusions. Usage is implied by the resource name rather than explicitly routed.

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